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1.  Changing associations of episiotomy and anal sphincter injury across risk strata: results of a population-based register study in Finland 2004–2011 
BMJ Open  2013;3(8):e003216.
Objectives
To evaluate the changing association between lateral episiotomy and obstetric anal sphincter injury (OASIS) for women with low and high baseline risk of OASIS.
Design
A population-based register study.
Setting
Data gathered from the Finnish Medical Birth Register for the years 2004−2011.
Participants
All women with spontaneous vaginal or vacuum-assisted singleton births in Finland (n=384 638).
Main outcome measure
OASIS incidence.
Results
During the study period, the incidence of OASIS increased from 1.3% to 1.7% in women with first vaginal births, including women admitted for first vaginal birth after a prior caesarean section and from 0.1% to 0.3% in women with at least one prior birth, whereas episiotomy rates declined from 56.7% to 45.5% and 10.1– 5.3%, respectively. At the study onset, when episiotomy was used more widely, it was negatively associated with OASIS in women with first vaginal births, but as episiotomy use declined it became positively associated with OASIS. Women with episiotomy were complicated by OASIS with clearly higher risk scores than women without episiotomy suggesting that episiotomy was clearly protective against OASIS. OASIS occurred with lower mean risk scores among women with and without episiotomy over time. However, OASIS incidences increased only among women with episiotomy, whereas it decreased or remained among women without episiotomy.
Conclusions
The cross-over effect between episiotomy and OASIS could be explained by increasing disparity in baseline OASIS risk between treated and untreated women, since episiotomy use declined most in women at low OASIS risk. Episiotomy rate can be safely reduced in low-risk women but interestingly along with the policy change the practice to cut the episiotomy became less protective among high-risk women.
doi:10.1136/bmjopen-2013-003216
PMCID: PMC3752051  PMID: 23955189
EPIDEMIOLOGY; OBSTETRICS
2.  Can the risk of obstetric anal sphincter injuries (OASIs) be predicted using a risk-scoring system? 
BMC Research Notes  2014;7:471.
Background
Perineal trauma involving the anal sphincter is an important complication of vaginal delivery. Prediction of anal sphincter injuries may improve the prevention of anal sphincter injuries. Our aim was to construct a risk scoring model to assist in both prediction and prevention of Obstetric Anal Sphincter Injuries (OASIs). We carried out an analysis of factors involved with OASIs, and tested the constructed model on new patient data.
Methods
Data on all vaginal deliveries over a 5 year period (2004–2008) was obtained from the electronic maternity record system of one institution in the UK. All risk factors were analysed using logistic regression analysis. Odds ratios for independent variables were then used to construct a risk scoring algorithm. This algorithm was then tested on subsequent vaginal deliveries from the same institution to predict the incidence of OASIs.
Results
Data on 16,920 births were analysed. OASIs occurred in 616 (3.6%) of all vaginal deliveries between 2004 and 2008. Significant (p < 0.05) variables that increased the risk of OASIs on multivariate analysis were: African-Caribbean descent, water immersion in labour, water birth, ventouse delivery, forceps delivery. The following variables remained independently significant in decreasing the risk of OASIs: South Asian descent, vaginal multiparity, current smoker, home delivery. The subsequent odds ratios were then used to construct a risk-scoring algorithm that was tested on a separate cohort of patients, showing a sensitivity of 52.7% and specificity of 71.1%.
Conclusions
We have confirmed known risk factors previously associated with OASIs, namely parity, birth weight and use of instrumentation during delivery. We have also identified several previously unknown factors, namely smoking status, ethnicity and water immersion. This paper identifies a risk scoring system that fulfils the criteria of a reasonable predictor of the risk of OASIs. This supersedes current practice where no screening is implemented other than examination at the time of delivery by a single examiner. Further prospective studies are required to assess the clinical impact of this scoring system on the identification and prevention of third degree tears.
doi:10.1186/1756-0500-7-471
PMCID: PMC4119183  PMID: 25056485
Anal sphincter; Perineal trauma; Risk factors; Third and fourth degree tears
3.  The Burden of OASIS Increases along with Socioeconomic Position – Register-Based Analysis of 980,733 Births in Finland 
PLoS ONE  2013;8(8):e73515.
Background
Obstetric anal sphincter injury (OASIS) has been identified as a major preventable risk factor for anal incontinence.
Objective
Aim was to measure national variation in incidence of OASIS by socioeconomic status (SES).
Methods
A retrospective population based case-control study using the data derived from the Finnish Medical Birth Register for the years 1991–2010. A total population of singleton vaginal births was reviewed. We calculated unadjusted incidences of OASIS stratified by SES and vaginal parity, and adjusted risks for OASIS in each social class, after controlling for parity, birthweight, mode of delivery, maternal age and maternal smoking. SES was recorded into five categories based on mother’s occupation at time of birth; upper white-collar workers such as physicians, lower white-collar workers such as nurses, blue-collar workers such as cleaners, others such as students, and cases with missing information.
Results
Seven per thousand (6,404 of 980,733) singleton births were affected by OASIS. In nulliparae the incidence of OASIS was 18% higher (adjusted OR 1.18 95% CI 1.04−1.34) for upper white-collar workers and 12% higher (adjusted OR 1.12 95% CI 1.02−1.24) for lower white-collar workers compared with blue-collar workers. Among women in these higher SES groups, 40% of the excess OASIS risk was explained by age, non-smoking, birthweight and mode of delivery. Despite the large effect of SES on OASIS, inclusion of SES in multivariable models caused only small changes in estimated adjusted effects for other established risk factors.
Conclusions
OASIS at the first vaginal delivery demonstrates a strong positive social gradient. Higher SES is associated with a number of risk factors for OASIS, including higher birthweight and non-smoking, but only 40% of the excess incidence is explained by these known risk factors. Further research should address other underlying causes including differences in lifestyle or environmental factors, and inequalities in healthcare provision.
doi:10.1371/journal.pone.0073515
PMCID: PMC3754956  PMID: 24013645
4.  The Association of Episiotomy with Obstetric Anal Sphincter Injury–A Population Based Matched Cohort Study 
PLoS ONE  2014;9(9):e107053.
Objectives
To estimate the independent association of episiotomy with obstetric anal sphincter injuries (OASIS) using first a cross-sectional and then a matched pair analysis.
Design
A matched cohort.
Setting
Data was gathered from the Finnish Medical Birth Register from 2004–2011.
Population
All singleton vaginal births (n = 303,758).
Methods
Women resulting matched pairs (n = 63,925) were matched based on baseline risk of OASIS defined based on parity (first or second/subsequent vaginal births), age, birth weight, mode of delivery, prior caesarean section, and length of active second stage of birth.
Results
In cross-sectional analysis episiotomy was associated with a 12% lower incidence of OASIS (adjusted odds ratio (aOR) 0.88, 95% confidence interval (CI) 0.80 to 0.98) in first vaginal births and with a 132% increased incidence of OASIS in second or subsequent vaginal births (aOR 2.32, 95% CI 1.77 to 3.03). In matched pair analysis episiotomy was associated with a 23% (aOR 0.77, 95% CI 0.69 to 0.86) lower incidence of OASIS in first vaginal births and a 61% (aOR 1.61, 95% CI 1.14 to 2.29) increased incidence of OASIS in second or subsequent vaginal births compared to women who gave birth without an episiotomy. The matched pair analysis showed a 12.5% and a 31.6% reduction in aORs of OASIS associated with episiotomy, respectively.
Conclusions
A matched pair analysis showed a substantial reduction in the aORs of OASIS with episiotomy, due to confounding by indication. This indicates that results of observational studies evaluating an association between episiotomy and OASIS should be interpreted with caution.
doi:10.1371/journal.pone.0107053
PMCID: PMC4159295  PMID: 25203655
5.  Up to seven-fold inter-hospital differences in obstetric anal sphincter injury rates- A birth register-based study in Finland 
BMC Research Notes  2010;3:345.
Background
The occurrence of obstetric anal sphincter injuries (OASIS) - which may have serious, long-term effects on affected women, including faecal incontinence, despite primary repair - varies widely between countries and have been chosen one of the indicators for patient safety in Organisation for Economic Cooperation and Development (OECD) countries and in Nordic countries.
Findings
The aim of the study was to assess risks of OASIS among five university teaching hospitals and 14 non-university central hospitals with more than 1,000 deliveries annually during 1997-2007 in Finland. Women with singleton vaginal deliveries divided into two populations consisting of all 168,637 women from five university hospitals and all 255,660 women from non-university hospitals, respectively, derived from population-based register. Primiparous and multiparous women with OASIS (n = 2,448) were compared in terms of possible risk factors to primiparous and multiparous women without OASIS, respectively, using stepwise logistic regression analysis. The occurrences of OASIS varied from 0.7% to 2.1% in primiparous and from 0.1% to 0.3% in multiparous women among the university hospitals. Three-fold inter-hospital differences in OASIS rates did not significantly change after adjustment for patient mix or the use of interventions. In non-university hospitals OASIS rates varied from 0.2% to 1.4% in primiparous and from 0.02% to 0.4% in multiparous women, and the results remained virtually unchanged after adjustment for known risks.
Conclusions
Up to 3.2-fold inter-hospital differences in OASIS risk demonstrates significant differences in the quality of Finnish obstetric care.
doi:10.1186/1756-0500-3-345
PMCID: PMC3022816  PMID: 21182773
6.  Anal incontinence, urinary incontinence and sexual problems in primiparous women – a comparison between women with episiotomy only and women with episiotomy and obstetric anal sphincter injury 
BMC Women's Health  2014;14(1):157.
Background
Obstetric anal sphincter injuries (OASIS) might cause anal incontinence (AI) and sexual dysfunction, and might be associated with urinary incontinence (UI). Episiotomy has been identified both as a risk and a protective factor of OASIS. Lately, episiotomies with specific characteristics have shown to be protective against the risk of OASIS. However, little is known about episiotomy characteristics and pelvic floor dysfunction. This study investigates AI, UI, and sexual problems in primiparous women with episiotomy, comparing women with and without OASIS. Associations between episiotomy characteristics and AI, UI, and sexual problems were assessed.
Methods
This is a matched case–control study investigating 74 women with one vaginal birth, all with an episiotomy. Among these, 37 women sustained OASIS and were compared to 37 women without OASIS. The two groups were matched for vacuum/forceps. AI, UI and sexual problem symptoms were obtained from St. Mark’s scoring-tool and self-administered questionnaires. The episiotomy characteristics were investigated and results assessed for the whole group.
Results
The mean time from birth was 34.5 months (range1.3-78.2) for those with OASIS and 25.9 months (range 7.0-57.4) for those without OASIS, respectively. More women with OASIS reported AI: 14 (38%) vs. 3 (8%) p = 0.05 (OR 4.66, 95% CI 1.34-16.33) as well as more problem with sexual desire p = 0.02 (OR 7.62, 95% CI 1.30-44.64) compared to women without OASIS. We found no association between episiotomy with protective characteristics and dysfunctions.
Conclusion
Women with OASIS had more AI and sexual problems than those without OASIS. Episiotomy characteristics varied greatly between the women. Episiotomy with protective characteristics was not associated with increased dysfunctions. OASIS should be avoided, and correct episiotomy used if indicated.
doi:10.1186/s12905-014-0157-y
PMCID: PMC4273460  PMID: 25511413
Obstetric anal sphincter injuries; Episiotomy characteristics; Anal incontinence; Urinary incontinence; Sexual problems
7.  Episiotomy characteristics and risks for obstetric anal sphincter injuries: a case-control study 
Bjog  2012;119(6):724-730.
Objectives
To investigate the association between the geometrical properties of episiotomy and obstetric anal sphincter injuries (OASIS) because episiotomies angled at 40–60° are associated with fewer OASIS than episiotomies with more acute angles.
Design
Case–control study.
Setting
University Hospital of North Norway, Tromsø and Nordland Hospital, Bodø, Norway.
Sample
Seventy-four women who had one vaginal birth and episiotomy. Cases (n = 37) have sustained OASIS at birth, while controls (n = 37) had not. The groups were matched for instrumental delivery.
Methods
Two groups of women with history of only one vaginal birth were compared. Episiotomy scar was identified and photographed and relevant measures were taken. Data were analysed using conditional logistic analysis.
Main outcome measures
Mean episiotomy angle, length, depth, incision point.
Results
The risk of sustaining OASIS decreased by 70% (odds ratio [OR] 0.30; 95% CI 0.14–0.66) for each 5.5-mm increase in episiotomy depth, decreased by 56% (OR 0.44; 95% CI 0.23–0.86) for each 4.5-mm increase in the distance from the midline to the incision point of the episiotomy, and decreased by 75% (OR 0.25; 95% CI 0.10–0.61) for each 5.5-mm increase in episiotomy length. Lastly, there was no difference in mean angle between groups but there was a “U-shaped” association between angle and OASIS (OR 2.09; 95% CI 1.02–4.28) with an increased risk (OR 9.00; 95% CI 1.1–71.0) of OASIS when the angle was either smaller than 15°or >60°.
Conclusion
The present study showed that scarred episiotomies with depth > 16 mm, length > 17 mm, incision point > 9 mm lateral of midpoint and angle range 30–60° are significantly associated with less risk of OASIS. Shrinkage of tissue must be considered.
doi:10.1111/j.1471-0528.2012.03293.x
PMCID: PMC3489037  PMID: 22390647
Episiotomy; episiotomy technique; obstetric anal sphincter injuries; vaginal birth
8.  Smoking during Pregnancy Is Associated with a Decreased Incidence of Obstetric Anal Sphincter Injuries in Nulliparous Women 
PLoS ONE  2012;7(7):e41014.
Background
Smoking is a modifiable lifestyle factor that has been shown to be associated with adverse perinatal outcomes and to have adverse health and dose-dependent connective tissue effects. The objective of this study was to examine whether smoking during pregnancy was associated with the incidence of obstetric anal sphincter injuries (OASIS) among six birthweight groups in singleton vaginal deliveries, considering nulliparous and multiparous women separately between 1997 and 2007 in Finland.
Methodology
A retrospective population-based register study. Populations included women with spontaneous singleton vaginal deliveries, consisting of all 213,059 nulliparous and all 288,391 multiparous women. Incidence of OASIS (n = 2,787) between smoking status groups was adjusted using logistic regression analyses.
Principal Findings
Of the nulliparous women, 13.1% were smokers, 3.6% had given up smoking during the first trimester of their pregnancy and 81.1% were non-smokers. Among these groups 0.7%, 0.9% and 1.1%, respectively suffered OASIS (p≤0.001). Nulliparous women who smoked had a 28% (95% CI 16–38%, p≤0.001) lower risk of OASIS compared to non-smokers, when adjusting for background variables. In multiparous women, the overall frequencies of OASIS were much lower (0.0–0.2%). A similar inverse relationship between OASIS rates and smoking was significant in pooled univariate analysis of multiparous women, but multivariate analysis revealed statistically insignificant results between non-smokers and smokers.
Conclusions
Nulliparous women who were smokers had a 28% lower incidence of OASIS. However, smoking during pregnancy cannot be recommended since it has shown to be associated with other adverse pregnancy outcomes and adverse health effects. The observed association warrants clinical repetition studies and, if confirmed, also in vitro studies focusing on connective tissue properties at a molecular and cellular level.
doi:10.1371/journal.pone.0041014
PMCID: PMC3397985  PMID: 22815899
9.  Incidence of and risk factors for perineal trauma: a prospective observational study 
Background
Our aim was to describe the range of perineal trauma in women with a singleton vaginal birth and estimate the effect of maternal and obstetric characteristics on the incidence of perineal tears.
Methods
We conducted a prospective observational study on all women with a planned singleton vaginal delivery between May and September 2006 in one obstetric unit, three freestanding midwifery-led units and home settings in South East England. Data on maternal and obstetric characteristics were collected prospectively and analysed using univariable and multivariable logistic regression. The outcome measures were incidence of perineal trauma, type of perineal trauma and whether it was sutured or not.
Results
The proportion of women with an intact perineum at delivery was 9.6% (125/1,302) in nulliparae, and 31.2% (453/1,452) in multiparae, with a higher incidence in the community (freestanding midwifery-led units and home settings). Multivariable analysis showed multiparity (OR 0.52; 95% CI: 0.30–0.90) was associated with reduced odds of obstetric anal sphincter injuries (OASIS), whilst forceps (OR 4.43; 95% CI: 2.02–9.71), longer duration of second stage of labour (OR 1.49; 95% CI: 1.13–1.98), and heavier birthweight (OR 1.001; 95% CI: 1.001–1.001), were associated with increased odds. Adjusted ORs for spontaneous perineal truama were: multiparity (OR 0.42; 95% CI: 0.32–0.56); hospital delivery (OR 1.48; 95% CI: 1.01–2.17); forceps delivery (OR 2.61; 95% CI: 1.22–5.56); longer duration of second stage labour (OR 1.45; 95% CI: 1.28–1.63); and heavier birthweight (OR 1.001; 95% CI: 1.000–1.001).
Conclusions
This large prospective study found no evidence for an association between many factors related to midwifery practice such as use of a birthing pool, digital perineal stretching in the second stage, hands off delivery technique, or maternal birth position with incidence of OASIS or spontaneous perineal trauma. We also found a low overall incidence of OASIS, and fewer second degree tears were sutured in the community than in the hospital settings. This study confirms previous findings of overall high incidence of perineal trauma following vaginal delivery, and a strong association between forceps delivery and perineal trauma.
doi:10.1186/1471-2393-13-59
PMCID: PMC3599825  PMID: 23497085
Vaginal delivery; Perineal trauma; OASIS; Prospective study
10.  Evaluation of the angled Episcissors-60® episiotomy scissors in spontaneous vaginal deliveries 
Background
Obstetric anal sphincter injuries (OASIs) are the leading cause of anal incontinence in women. Episiotomies with a postdelivery suture angle of less than 30° to the midline are more likely to injure the anal sphincter directly, while those with a suture angle of more than 60° are associated with increased incidence of OASIs, as they do not relieve the pressure on the perineum. A safe zone of 40°–60° has been proposed. Recently, two new types of episiotomy scissors (Episcissors-60® Straight version and angled version) were introduced to ensure a standardized cutting angle of 60° to the midline. We audited our results with the angled Episcissors-60 in spontaneous vaginal deliveries.
Materials and methods
Consecutive patients delivering in two private maternity hospitals in Thane, India undergoing clinically indicated episiotomies were included. Only patients delivering spontaneously were included. The scissors were introduced vaginally at crowning, and aligned to orient the guide limb vertically from the posterior fourchette to the anus. While a single cut was preferred, a stagger cut was needed for some women. Postdelivery angles were measured by placing a protractor transparency on the perineum after delivery and marking the angle with an indelible ink pen. Per rectal examination was performed prior to suturing to detect OASIs.
Results
A total of 25 women underwent clinically indicated episiotomies. Of these, 16 women were nulliparous, eight women were para 1, and one woman was a para 2. One woman had a vaginal breech delivery (para 2), and the rest were cephalic vertex deliveries. The average age was 27 (range 20–35) years. The median birth weight was 2,800 g (standard deviation 312 g, interquartile range 2,500–3,000 g). The median postdelivery suture angle of the episiotomy was 50° (standard deviation 3.5°, interquartile range 48°–54°, range 45°–55°). No cases of OASI were detected in this series.
Conclusion
The Episcissors-60 angled version demonstrated a postdelivery suture angle of 50° in a cohort of Indian women undergoing spontaneous vaginal deliveries.
doi:10.2147/MDER.S66901
PMCID: PMC4124071  PMID: 25114598
60° episiotomy; anal incontinence; episiotomy scissors; Episcissors-60; obstetric anal sphincter injuries (OASIs); Indian women
11.  A modified surgical approach to women with obstetric anal sphincter tears by separate suturing of external and internal anal sphincter. A modified approach to obstetric anal sphincter injury 
Background
Long-term results after obstetric anal sphincter injury (OASI) are poor. We aimed to improve the long-term outcome after OASI by lessening symptoms of anal incontinence.
Methods
In a prospective study at Malmö University Hospital, twenty-six women with at least grade 3B OASI were classified and sutured in a systematic way, including separate suturing of the internal and external sphincter muscles with monofilament absorbable sutures. The principal outcome assessed by answers given to six questions, was a difference in anal incontinence score, between the study group and two control groups (women with prior OASI [n = 180] and primiparous women delivered vaginally without a diagnose of OASI [n = 100]).
Results
An anal incontinence score of zero (i.e., no symptoms) was found in 74% of the study group, 47% of the OASI control group, and 66% of the vaginal control group (p = 0.02 and 0.5, as compared to the study group).
Conclusions
A modified suturing technique was followed by significant improved one-year symptoms of anal incontinence as compared to historical cases.
doi:10.1186/1471-2393-10-51
PMCID: PMC2949785  PMID: 20828380
12.  Cutting a mediolateral episiotomy at the correct angle: evaluation of a new device, the Episcissors-60 
Background
Anal incontinence is nine times more prevalent in women than in men due to obstetric anal sphincter injury (OASI). OASI is linked to midline episiotomies and mediolateral episiotomies with post-delivery angles of <30 and >60 degrees. Studies show that doctors and midwives are unable to correctly “eyeball” the safe angle required due to perineal stretching by the fetal head at crowning. A new scissor instrument (Episcissors-60) was devised to allow cutting a mediolateral episiotomy at a fixed angle of 60 degrees from the perineal midline.
Methods
Scissors with a marker guide limb pointing towards the anus were devised, ensuring an angle of 60 degrees between the scissor blades and the guide limb. This device was initially tested in models. Post-delivery angles were recorded on transparencies and analyzed by an author blinded to clinical details. Accoucheurs were asked to rate the ease of use on a 5-point scale.
Results
Of the 17 women, 14 delivered with ventouse, two with forceps, and one with sequential ventouse–forceps. Indications for instrumental delivery were suboptimal cardiotocogram and/or prolonged second stage of labor. Mean birth weight was 3.41 (2.92–4.12) kg. A mean post-delivery angle of 42.4±7 (range 30–60, median 43) degrees (95% confidence interval 38.8–46) was achieved with the Episcissors-60 instrument. Eighty-eight percent of clinicians agreed or strongly agreed that the scissors were easy to use.
Conclusion
The Episcissors-60 delivered a consistent post-delivery angle of 43 degrees. They could replace “eyeballing” when performing mediolateral episiotomies and form part of a preventative strategy to reduce OASI.
doi:10.2147/MDER.S60056
PMCID: PMC3933714  PMID: 24570598
60 degree episiotomy; anal incontinence; episiotomy scissors; mediolateral episiotomy; obstetric anal sphincter injury; OASI
13.  The impact of an intervention programme employing a hands-on technique to reduce the incidence of anal sphincter tears: interrupted time-series reanalysis 
BMJ Open  2013;3(10):e003355.
Objective
To re-evaluate previously published findings from an uncontrolled before–after evaluation of an intervention programme to reduce the incidence of anal sphincter tears. A key component of the programme was the use of a hands-on technique where the birth attendant presses the neonate's head during the final stage of delivery while simultaneously supporting the woman's perineum with the other hand.
Design
Interrupted time-series analysis using segmented regression modelling.
Setting
Obstetric departments of five Norwegian hospitals.
Participants
All women giving births vaginally in the study hospitals, 2002–2008.
Methods
The main data source was the Medical Birth Registry of Norway. We estimated the change in incidence of anal sphincter tears before and after implementation of the intervention in the five intervention hospitals, taking into account the trends in incidence before and after implementation.
Main outcome measures
Incidence of anal sphincter tears and episiotomies.
Results
There were 75 543 registered births at the five included hospitals. We found a 2% absolute reduction in incidence of anal sphincter tears associated with the hospital intervention programme, representing almost a halving in the number of women experiencing serious anal sphincter tears. This is a substantially smaller estimate than previously reported. However, it does represent a highly significant decrease in anal sphincter injuries. The programme was also associated with a significant increase in episiotomies.
Conclusions
The intervention programme was associated with a significant reduction in the incidence of obstetric anal sphincter tears. Still, the findings should be interpreted with caution as they seem to contradict the findings from randomised controlled studies of similar interventions.
doi:10.1136/bmjopen-2013-003355
PMCID: PMC3808759  PMID: 24154515
OBSTETRICS; STATISTICS & RESEARCH METHODS
14.  Perineal care 
Clinical Evidence  2011;2011:1401.
Introduction
Over 85% of women having a vaginal birth suffer some perineal trauma. Spontaneous tears requiring suturing are estimated to occur in at least a third of women in the UK and US, with anal sphincter tears in 0.5% to 7% of women. Perineal trauma can lead to long-term physical and psychological problems.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of intrapartum surgical and non-surgical interventions on rates of perineal trauma? What are the effects of different methods and materials for primary repair of first- and second-degree tears and episiotomies? What are the effects of different methods and materials for primary repair of obstetric anal sphincter injuries (third- and fourth-degree tears)? We searched: Medline, Embase, The Cochrane Library, and other important databases up to March 2010 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 38 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review we present information relating to the effectiveness and safety of the following interventions: active pushing, spontaneous pushing, and sustained breath-holding (Valsalva) method of pushing; continuous support during labour; conventional suturing; different methods and materials for primary repair of obstetric anal sphincter injuries; episiotomies (midline and mediolateral incisions); epidural analgesia; forceps; methods of delivery ("hands-on" method, "hands poised"); water births; non-suturing of muscle and skin (or perineal skin alone); passive descent in the second stage of labour; positions (supine or lithotomy positions, upright position during delivery); restrictive or routine use of episiotomy; sutures (absorbable synthetic sutures, catgut sutures, continuous sutures, interrupted sutures); and vacuum extraction.
Key Points
Over 85% of women having a vaginal birth suffer some perineal trauma. Spontaneous tears requiring suturing are estimated to occur in at least one third of women in the UK and US, with anal sphincter tears in 0.5% to 7% of women.Risk factors include first vaginal delivery, large or malpositioned baby, older or white mother, abnormal collagen synthesis, poor nutritional state, and forceps delivery.
Perineal trauma can lead to long-term physical and psychological problems. Up to 10% of women continue to have long-term perineal pain; up to 25% will have dyspareunia or urinary problems, and up to 10% will report faecal incontinence.
Restricting routine use of episiotomy reduces the risk of posterior perineal trauma. Using episiotomies only when there are clear maternal or fetal indications increases the likelihood of maintaining an intact perineum, and does not increase the risk of third-degree tears.
We don't know whether pain or wound dehiscence are less likely to occur with midline episiotomy compared with mediolateral incision. Midline incisions may be more likely to result in severe tears, although we can't be sure about this.
Instrumental delivery increases the risk of perineal trauma. The risk of instrumental delivery is increased after epidural analgesia. Vacuum extraction reduces the rate of severe perineal trauma compared with forceps delivery, but increases the risk of cephalhaematoma and retinal haemorrhage in the newborn.
Continuous support during labour reduces the rate of assisted vaginal births, and thus the rate of perineal trauma.
The "hands-poised" delivery method is associated with lower rates of episiotomy, but increased rates of short-term pain and manual removal of the placenta. Likewise, an upright position during delivery is associated with lower rates of episiotomy, but no significant difference in overall rates of perineal trauma.
Non-suturing of first- and second-degree tears (perineal skin and muscles) may be associated with reduced wound healing up to 3 months after birth. However, leaving the perineal skin alone unsutured (vagina and perineal muscles sutured) reduces dyspareunia and may reduce pain at up to 3 months.
Absorbable synthetic sutures for repair of first- and second-degree tears and episiotomies are less likely to result in long-term pain than catgut sutures. Rapidly absorbed synthetic sutures reduce the need for suture removal. Continuous sutures reduce short-term pain.
Early primary overlap repair for third- and fourth-degree anal sphincter tears seems to be associated with lower risks for faecal urgency and anal incontinence symptoms than end-to-end approximation.
We don't know whether immersion in water during the first or second stage of labour has any effect on rates of perineal trauma or whether passive descent is better than active pushing.
It is unclear whether the sustained breath holding (Valsalva) method is more effective at reducing rates of perineal trauma compared with exhalatory or spontaneous pushing.
PMCID: PMC3275301  PMID: 21481287
15.  Perineal care 
Clinical Evidence  2008;2008:1401.
Introduction
Over 85% of women having a vaginal birth suffer some perineal trauma. Spontaneous tears requiring suturing are estimated to occur in at least a third of women in the UK and USA, with anal sphincter tears in 0.5% to 7% of women. Perineal trauma can lead to long-term physical and psychological problems.
Methods and outcomes
We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of intrapartum surgical and non-surgical interventions on rates of perineal trauma? What are the effects of different methods and materials for primary repair of first- and second-degree tears and episiotomies? What are the effects of different methods and materials for primary repair of obstetric anal sphincter injuries (third- and fourth-degree tears)? We searched: Medline, Embase, The Cochrane Library, and other important databases up to April 2007 (BMJ Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).
Results
We found 38 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.
Conclusions
In this systematic review we present information relating to the effectiveness and safety of the following interventions: active pushing, spontaneous pushing, and sustained breath-holding (Valsalva) method of pushing; continuous support during labour; conventional suturing; different methods and materials for primary repair of obstetric anal sphincter injuries; episiotomies (midline and mediolateral incisions); epidural analgesia; forceps; methods of delivery ("hands-on" method, "hands poised"); water births; non-suturing of muscle and skin (or perineal skin alone); passive descent in the second stage of labour; positions (supine or lithotomy positions, upright position during delivery); restrictive or routine use of episiotomy; sutures (absorbable synthetic sutures, catgut sutures, continuous sutures, interrupted sutures); and vacuum extraction.
Key Points
Over 85% of women having a vaginal birth suffer some perineal trauma. Spontaneous tears requiring suturing are estimated to occur in at least one third of women in the UK and USA, with anal sphincter tears in 0.5% to 7% of women.Risk factors include first vaginal delivery, large or malpositioned baby, older or white mother, abnormal collagen synthesis, poor nutritional state, and forceps delivery.
Perineal trauma can lead to long-term physical and psychological problems. Up to 10% of women continue to have long-term perineal pain; up to 25% will have dyspareunia or urinary problems, and up to 10% will report faecal incontinence.
Restricting routine use of episiotomy reduces the risk of posterior perineal trauma. Using episiotomies only when there are clear maternal or fetal indications increases the likelihood of maintaining an intact perineum, and does not increase the risk of third-degree tears.
We don't know whether pain or wound dehiscence are less likely to occur with midline episiotomy compared with mediolateral incision. Midline incisions may be more likely to result in severe tears, although we can't be sure about this.
Instrumental delivery increases the risk of perineal trauma. The risk of instrumental delivery is increased after epidural analgesia. Vacuum extraction reduces the rate of severe perineal trauma compared with forceps delivery, but increases the risk of cephalhaematoma and retinal haemorrhage in the newborn.
Continuous support during labour reduces the rate of assisted vaginal births, and thus the rate of perineal trauma.
The ‘hands-poised' delivery method is associated with lower rates of episiotomy, but increased rates of short-term pain and manual removal of the placenta. Likewise, an upright position during delivery is associated with lower rates of episiotomy, but no significant difference in overall rates of perineal trauma.
Non-suturing of first- and second-degree tears (perineal skin and muscles) may be associated with reduced wound healing up to 3 months after birth. However, leaving the perineal skin alone unsutured (vagina and perineal muscles sutured) reduces dyspareunia and may reduce pain at up to 3 months.
Absorbable synthetic sutures for repair of first- and second-degree tears and episiotomies are less likely to result in long-term pain compared with catgut sutures. Rapidly absorbed synthetic sutures reduces the need for suture removal. Continuous sutures reduce short-term pain.
Early primary overlap repair forthird- and fourth-degree anal sphincter tears seems to be associated with lower risks for faecal urgency and anal incontinence symptoms .
We dont know whether immersion in water during the first or second stage of labour has any effect on rates of perineal trauma.
PMCID: PMC2907946  PMID: 19445799
16.  Outcome of repair of obstetric anal sphincter injuries after three years 
Objective
To prospectively assess change in bowel symptoms and quality of life (QoL) approximately 3 years after primary repair of obstetric anal sphincter injuries (OASIS).
Methods
Between July 2002 and December 2007 women who attended the perineal clinic at Croydon University Hospital, UK, 9 weeks following primary repair of OASIS were asked to complete the Manchester Health Questionnaire and a questionnaire to obtain a St Mark incontinence score. All women had endoanal scans at this visit. In June 2008 all women were asked to complete the questionnaires again.
Results
Of 344 patients who responded to the questionnaires and were included in the analysis, long-term symptoms of fecal urgency, flatus incontinence, and fecal incontinence occurred in 62 (18.0%), 52 (15.1%), and 36 (10.5%), respectively. Overall, there was a significant improvement in fecal urgency (P < 0.001) and flatus incontinence (P < 0.001) from 9 weeks to 3 years. Of 31 women with fecal incontinence symptoms at early follow-up, 28 were asymptomatic at 3 years. However, 33 women developed de novo symptoms. The only predictors of fecal incontinence at 3 years were fecal urgency at 9 weeks (OR 4.65; 95% CI, 1.38–15.70) and a higher St Mark score (OR 1.40; 95% CI, 1.09–1.80).
Conclusion
Following primary repair of OASIS, the majority of symptoms and QoL significantly improve, unless there is a persistent anal sphincter defect. This highlights the importance of adequate repair.
doi:10.1016/j.ijgo.2014.04.013
PMCID: PMC4175217  PMID: 25097141
Bowel symptoms; Childbirth; Endoanal scan; Fecal incontinence; Obstetric anal sphincter injuries; Third-degree tears; Vaginal delivery
17.  Management of obstetric anal sphincter injury: a systematic review & national practice survey 
Background
We aim to establish the evidence base for the recognition and management of obstetric anal sphincter injury (OASI) and to compare this with current practice amongst UK obstetricians and coloproctologists.
Methods
A systematic review of the literature and a postal questionnaire survey of consultant obstetricians, trainee obstetricians and consultant coloproctologists was carried out.
Results
We found a wide variation in experience of repairing acute anal sphincter injury. The group with largest experience were consultant obstetricians (46.5% undertaking ≥ 5 repairs/year), whilst only 10% of responding colorectal surgeons had similar levels of experience (p < 0.001). There was extensive misunderstanding in terms of the definition of obstetric anal sphincter injuries. Overall, trainees had a greater knowledge of the correct classification (p < 0.01). Observational studies suggest that a new 'overlap' repair using PDS sutures with antibiotic cover gives better functional results. However, our literature search found only one randomised controlled trial (RCT) on the technique of repair of OASI, which showed no difference in incidence of anal incontinence at three months. Despite this, there was a wide variation in practice, with 337(50%) consultants, 82 (55%) trainees and 80 (89%) coloproctologists already using the 'overlap' method for repair of a torn EAS (p < 0.001). Although over 50% of colorectal surgeons would undertake long-term follow-up of their patients, this was the practice of less than 10% of obstetricians (p < 0.001). Whilst over 70% of coloproctologists would recommend an elective caesarean section in a subsequent pregnancy, only 22% of obstetric consultants and 14% of trainees (p < 0.001).
Conclusion
An agreed classification of OASI, development of national guidelines, formalised training, multidisciplinary management and further definitive research is strongly recommended.
doi:10.1186/1472-6963-2-9
PMCID: PMC116576  PMID: 12006105
18.  OBSTETRIC TRAUMA, PELVIC FLOOR INJURY AND FECAL INCONTINENCE: A POPULATION-BASED CASE-CONTROL STUDY 
Background and Aims
Current concepts based on referral center data suggest that pelvic floor injury from obstetric trauma is a major risk factor for fecal incontinence (FI) in women. In contrast, a majority of community women only develop FI decades after vaginal delivery, and obstetric events are not independent risk factors for FI. However, obstetric events are imperfect surrogates for anal and pelvic floor injury, which is often clinically occult. Hence, our objectives were to evaluate the relationship between prior obstetric events, pelvic floor injury, and FI among community women.
Design
In this nested case-control study of 68 women with FI (cases; mean age 57y) and 68 age-matched controls from a population-based cohort in Olmsted County, MN, pelvic floor anatomy and motion during voluntary contraction and defecation were assessed by MRI. Obstetric events and bowel habits were recorded.
Results
By multivariable analysis, internal sphincter injury (cases-28%, controls-6%; odds ratio [OR], 8.8; 95% CI, 2.3–34) and reduced perineal descent during defecation (cases-2.6 ± 0.2 cm, controls-3.1 ± 0.2 cm; OR, 1.7; 95% CI, 1.2–2.4) increased FI risk, but external sphincter injury (cases-25%, controls-4%;p < 0.005) was not independently predictive. Puborectalis injury was associated (p<0.05) with impaired anorectal motion during squeeze, but was not independently associated with FI. Grade 3–4 episiotomy (OR, 3.9; 95% CI, 1.4–11) but not other obstetric events increased the risk for pelvic floor injury. Heavy smoking (≥ 20 pack-years) was associated (p=0.052) with external sphincter atrophy.
Conclusions
State-of-the-art imaging techniques reveal pelvic floor injury or abnormal anorectal motion in a minority of community women with FI. Internal sphincter injury and reduced perineal descent during defecation are independent risk factors for FI. In addition to grade 3–4 episiotomy, smoking may be a potentially preventable, risk factor for pelvic floor injury.
doi:10.1038/ajg.2012.45
PMCID: PMC3509345  PMID: 22415196
anal sphincter; epidemiology; anal incontinence; imaging; risk factors
19.  Midwives’ lived experience of a birth where the woman suffers an obstetric anal sphincter injury - a phenomenological study 
Background
The occurrence of obstetric anal sphincter injuries (OASIS) has increased in most high-income countries during the past twenty years. The consequences of these injuries can be devastating for women and have an impact on their daily life and quality of health. The aim of this study was to obtain a deeper understanding of midwives’ lived experiences of attending a birth in which the woman gets an obstetric anal sphincter injury.
Methods
A qualitative study using phenomenological lifeworld research design. The data were collected through in-depth interviews with 13 midwives.
Results
The essential meaning of the phenomenon was expressed as a deadlock difficult to resolve between a perceived truth among midwives that a skilled midwife can prevent severe perineal trauma and at the same time a coexisting more complex belief. The more complex belief is that sphincter injuries cannot always be avoided. The midwives tried to cope with their feelings of guilt and wanted to find reasons why the injury occurred. A fear of being exposed and judged by others as severely as they judged themselves hindered the midwives from sharing their experience. Ultimately the midwives accepted that the injury had occurred and moved on without any definite answers.
Conclusions
Being caught between an accepted truth and a more complex belief evoked various emotions among the midwives. Feelings of guilt, shame and the midwife’s own suspicion that she is not being professionally competent were not always easy to share. This study shows the importance of creating a safe working environment in which midwives can reflect on and share their experiences to continue to develop professionally. Further research is needed to implement and evaluate the effect of reflective practices in relation to midwifery care and whether this could benefit women in childbirth.
doi:10.1186/1471-2393-14-258
PMCID: PMC4129100  PMID: 25086994
Obstetric anal sphincter injury; Midwives’ lived experiences; Phenomenology; Reflective lifeworld research; Reflection
20.  Prevalence and Risk Indicators for Anal Incontinence among Pregnant Women 
ISRN Obstetrics and Gynecology  2013;2013:947572.
The aim of this study was to assess the prevalence and risk factors of anal incontinence in an unselected pregnant population at second trimester. A survey of pregnant women attending a routine ultrasound examination was conducted in a university hospital in Oslo, Norway. A questionnaire consisting of 105 items concerning anal incontinence (including St. Mark's score), urinary incontinence, medication use, and comorbidity was posted to women when invited to the ultrasound examination. Results. Prevalence of self-reported anal incontinence (St. Mark's score ≥ 3) was the lowest in the group of women with a previous cesarean section only (6.4%) and the highest among women with a previous delivery complicated by obstetric anal sphincter injury (24.4%). Among nulliparous women the prevalence of anal incontinence was 7.7% and was associated to low educational level and comorbidity. Prevalence of anal incontinence increased with increasing parity. Urinary incontinence was associated with anal incontinence in all parity groups. Conclusions. Anal incontinence was most frequent among women with a history of obstetric anal sphincter injury. Other obstetrical events had a minor effect on prevalence of anal incontinence among parous women. Prevention of obstetrical sphincter injury is likely the most important factor for reducing bothersome anal incontinence among fertile women.
doi:10.1155/2013/947572
PMCID: PMC3681258  PMID: 23819058
21.  Maternal Body Mass Index and Risk of Obstetric Anal Sphincter Injury 
BioMed Research International  2014;2014:395803.
Objective. To estimate the association between maternal obesity and risk of three different degrees of severity of obstetric anal sphincter injury. Methods. The study population consisted of 436,482 primiparous women with singleton term vaginal cephalic births between 1998 and 2011 identified in the Swedish Medical Birth Registry. Women were grouped into six categories of BMI. BMI 18.5–24.9 was set as reference. Primary outcome was third-degree perineal laceration, partial or total, and fourth-degree perineal laceration. Adjustments were made for year of delivery, maternal age, fetal head position at delivery, infant birth weight and instrumental delivery. Results. The overall prevalence of third- or four-degree anal sphincter injury was 6.6% (partial anal sphincter injury 4.6%, total anal sphincter injury 1.2%, unclassified as either partial and total 0.2%, or fourth degree lacerations 0.6%). The risk for a partial, total, or a fourth-degree anal sphincter injury decreased with increasing maternal BMI most pronounced for total anal sphincter injury where the risk among morbidly obese women was half that of normal weight women, OR 0.47 95% CI 0.28–0.78. Conclusion. Obese women had a favourable outcome compared to normal weight women concerning serious pelvic floor damages at birth.
doi:10.1155/2014/395803
PMCID: PMC4009284  PMID: 24839604
22.  Anal incontinence after childbirth 
Background
Incontinence of stool and flatus are frequent complications of childbirth. We examined the prevalence and possible causes of these adverse outcomes in a large cohort of women.
Methods
We studied 949 pregnant women who gave birth in 5 hospitals in 1995/96 in the province of Quebec. These women, participants in a randomized controlled trial of prenatal perineal massage, completed a self-administered questionnaire 3 months after giving birth.
Results
Three months after delivery 29 women (3.1%) reported incontinence of stool, and 242 (25.5%) had involuntary escape of flatus. Incontinence of stool was more frequent among women who delivered vaginally and had third- or fourth-degree perineal tears than among those who delivered vaginally and had no anal sphincter tears (7.8% v. 2.9%). Forceps delivery (adjusted risk ratio [RR] 1.45, 95% confidence interval [CI] 1.01–2.08) and anal sphincter tears (adjusted RR 2.09, 95% CI 1.40–3.13) were independent risk factors for incontinence of flatus or stool or both. Anal sphincter injury was strongly and independently associated with first vaginal birth (RR 39.2, 95% CI 5.4–282.5), median episiotomy (adjusted RR 9.6, 95% CI 3.2–28.5), forceps delivery (adjusted RR 12.3, 95% CI 3.0–50.4) and vacuum-assisted delivery (adjusted RR 7.4, 95% CI 1.9–28.5) but not with birth weight (adjusted RR for birth weight 4000 g or more: 1.4, 95% CI 0.6–3.0) or length of the second stage of labour (adjusted RR for second stage 1.5 hours or longer compared with less than 0.5 hours: 1.2, 95% CI 0.5–2.7).
Interpretation
Anal incontinence is associated with forceps delivery and anal sphincter laceration. Anal sphincter laceration is strongly predicted by first vaginal birth, median episiotomy, and forceps or vacuum delivery but not by birth weight or length of the second stage of labour.
PMCID: PMC99311  PMID: 11868640
23.  Assessing the association of oxytocin augmentation with obstetric anal sphincter injury in nulliparous women: a population-based, case–control study 
BMJ Open  2014;4(7):e004592.
Objective
To assess the association of oxytocin augmentation with obstetric anal sphincter injury among nulliparous women.
Design
Population-based, case–control study.
Setting
Primary and secondary teaching hospital serving a Norwegian region.
Population
15 476 nulliparous women with spontaneous start of labour, single cephalic presentation and gestation ≥37 weeks delivering vaginally between 1999 and 2012.
Methods
Based on the presence or absence of oxytocin augmentation, episiotomy, operative vaginal delivery and birth weight (<4000 vs ≥4000 g), we modelled in logistic regression the best fit for prediction of anal sphincter injury. Within the modified model of main exposures, we tested for possible confounding, and interactions between maternal age, ethnicity, occiput posterior position and epidural analgaesia.
Main outcome measure
Obstetric anal sphincter injury.
Results
Oxytocin augmentation was associated with a higher OR of obstetric anal sphincter injuries in women giving spontaneous birth to infants weighing <4000 g (OR 1.8; 95% CI 1.5 to 2.2). Episiotomy was not associated with sphincter injuries in spontaneous births, but with a lower OR in operative vaginal deliveries. Spontaneous delivery of infants weighing ≥4000 g was associated with a threefold higher OR, and epidural analgaesia was associated with a 30% lower OR in comparison to no epidural analgaesia.
Conclusions
Oxytocin augmentation was associated with a higher OR of obstetric anal sphincter injuries during spontaneous deliveries of normal-size infants. We observed a considerable effect modification between the most important factors predicting anal sphincter injuries in the active second stage of labour.
doi:10.1136/bmjopen-2013-004592
PMCID: PMC4120359  PMID: 25059967
Epidemiology
24.  Methods and consequences of changes in use of episiotomy. 
BMJ : British Medical Journal  1994;309(6964):1255-1258.
OBJECTIVES--To evaluate the use of feedback by graphical profiles of rates of episiotomy and the impact on clinical practice and perineal state after spontaneous vaginal deliveries assisted by midwives with different attitudes towards episiotomy. DESIGN--Observation period in labour ward followed by feedback to midwives about their own and other midwives' use of episiotomies. The periods before and after the intervention were compared. SUBJECTS--All women (n = 3919) delivering during the two periods who had been assisted by one of 30 midwives; each midwife supervised at least 20 deliveries during each period. MAIN OUTCOME MEASURES--Overall rates of episiotomies and indications, incidence of intact perineums, perineal lacerations, and tears of anal sphincter. RESULTS--The overall rate of episiotomy during the observation period was 37.1% (615). During the second period the rate was 6.6% lower (95% confidence interval 3.6% to 9.6%), corresponding to a relative decrease of 17.8% (10.1% to 24.7%). Higher rates of episiotomy during the observation period were associated with larger reductions in the second period. The decrease could be explained by less use of episiotomy in deliveries with rigid perineum or impending perineal tear. Compared with the observation period, in the second period 3.2% more women (0.3% to 6.3%) had an intact perineum after delivery and 3.4% (0.4% to 6.2%) experienced perineal tears. The overall incidence of tears of the anal sphincter remained unchanged. Women had a slightly reduced incidence of tears of the anal sphincter, however, if they were delivered by midwives who reduced a medium or high initial rate of episiotomy and a tendency towards an increased incidence of tears if they were assisted by midwives who reduced low initial rates (around 20%) of episiotomy. CONCLUSIONS--Changes in the use of episiotomy induced by awareness of clinical practice among midwives seem to increase the incidence of parturients with intact perineum without a concomitant rise in tears of the anal sphincter. To avoid the increase of such tears these changes should probably be restricted to midwives with rates of episiotomies above 30%.
PMCID: PMC2541821  PMID: 7888844
25.  Attractive toxic sugar bait (ATSB) methods decimate populations of Anopheles malaria vectors in arid environments regardless of the local availability of favoured sugar-source blossoms 
Malaria Journal  2012;11:31.
Background
Attractive toxic sugar bait (ATSB) methods are a new and promising "attract and kill" strategy for mosquito control. Sugar-feeding female and male mosquitoes attracted to ATSB solutions, either sprayed on plants or in bait stations, ingest an incorporated low-risk toxin such as boric acid and are killed. This field study in the arid malaria-free oasis environment of Israel compares how the availability of a primary natural sugar source for Anopheles sergentii mosquitoes: flowering Acacia raddiana trees, affects the efficacy of ATSB methods for mosquito control.
Methods
A 47-day field trial was conducted to compare impacts of a single application of ATSB treatment on mosquito densities and age structure in isolated uninhabited sugar-rich and sugar-poor oases relative to an untreated sugar-rich oasis that served as a control.
Results
ATSB spraying on patches of non-flowering vegetation around freshwater springs reduced densities of female An. sergentii by 95.2% in the sugar-rich oasis and 98.6% in the sugar-poor oasis; males in both oases were practically eliminated. It reduced daily survival rates of female An. sergentii from 0.77 to 0.35 in the sugar-poor oasis and from 0.85 to 0.51 in the sugar-rich oasis. ATSB treatment reduced the proportion of older more epidemiologically dangerous mosquitoes (three or more gonotrophic cycles) by 100% and 96.7%, respectively, in the sugar-poor and sugar-rich oases. Overall, malaria vectorial capacity was reduced from 11.2 to 0.0 in the sugar-poor oasis and from 79.0 to 0.03 in the sugar-rich oasis. Reduction in vector capacity to negligible levels days after ATSB application in the sugar-poor oasis, but not until after 2 weeks in the sugar-rich oasis, show that natural sugar sources compete with the applied ATSB solutions.
Conclusion
While readily available natural sugar sources delay ATSB impact, they do not affect overall outcomes because the high frequency of sugar feeding by mosquitoes has an accumulating effect on the probability they will be attracted to and killed by ATSB methods. Operationally, ATSB methods for malaria vector control are highly effective in arid environments regardless of competitive, highly attractive natural sugar sources in their outdoor environment.
doi:10.1186/1475-2875-11-31
PMCID: PMC3293779  PMID: 22297155
Sugar feeding; Vectorial capacity; Malaria; Attractive toxic sugar baits (ATSB); Outdoor mosquito control; Anopheles sergentii

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