Fetal growth restriction is associated with adverse perinatal outcome but is often not recognised antenatally, and low birthweight centiles based on population norms are used as a proxy instead. This study compared the association between neonatal morbidity and fetal growth status at birth as determined by customised birthweight centiles and currently used centiles based on population standards.
Retrospective cohort study.
Referral hospital, Barcelona, Spain.
A cohort of 13 661 non‐malformed singleton deliveries.
Both population‐based and customised standards for birth weight were applied to the study cohort. Customised weight centiles were calculated by adjusting for maternal height, booking weight, parity, ethnic origin, gestational age at delivery and fetal sex.
Main outcome measures
Newborn morbidity and perinatal death.
The association between smallness for gestational age (SGA) and perinatal morbidity was stronger when birthweight limits were customised, and resulted in an additional 4.1% (n = 565) neonates being classified as SGA. Compared with non‐SGA neonates, this newly identified group had an increased risk of perinatal mortality (OR 3.2; 95% CI 1.6 to 6.2), neurological morbidity (OR 3.2; 95% CI 1.7 to 6.1) and non‐neurological morbidity (OR 8; 95% CI 4.8 to 13.6).
Customised standards improve the prediction of adverse neonatal outcome. The association between SGA and adverse outcome is independent of the gestational age at delivery.
fetal growth restriction; neonatal morbidity; birthweight
UK-born infants of South Asian ethnic origin are known to have lower birthweights than their White British counterparts. When plotted on currently used birthweight charts they can be misclassified as small for gestational age. Similarly, large for gestational age infants can be missed. This has important clinical implications in their management.
To create birthweight centile charts for the UK-born South Asian infants to identify true small and large for gestational age infants.
A retrospective cross-sectional analysis of infants born 1 January 2003 to 31 December 2006 was undertaken. The birthweights of the South Asian and White British infants were compared. The LMS method was used to construct centile charts for the South Asian infants.
24,274 White British and 7,190 South Asian infants were included in the analysis. Overall, the South Asian males were 9–15% lighter than the White British males and the South Asian females were 9–13% lighter than the White British females. At term, the median birthweight for South Asian males was 329 g lower than that for White British males and for South Asian females 295 g less than the White British females.
There are significant differences in the birthweights of White British and UK-born South Asian infants. Hence the standard birthweight centile charts which were designed using the birthweight data of White British infants appear to misclassify a proportion of South Asian infants. Use of ethnic specific birthweight charts would allow better detection of truly growth-restricted and macrosomic South Asian infants.
Birthweight; Centile; Ethnicity
The birthweights of 100 infants with erythroblastosis were carefully matched as to sex, gestational age, and parity with the birthweights of 200 control infants born during the same period. At all gestational ages the average birthweight of the affected infants was below that of the controls, the average reduction being 227 g. The more severely affected infants tended to be at a lower centile for birthweight than were the mildly affected ones. The relationships between maternal serum folate, cord blood serum folate, and centile for birthweight among affected infants were also studied. There was a strong correlation between low maternal serum folate and the incidence of small-for-dates babies among the affected infants. There was also a strong correlation between maternal and cord blood serum folate values. There was a lack of correlation between maternal serum folate and cord blood haemoglobin. It is concluded that infants with erythroblastosis are lighter than controls and that the reason for this may be a shortage of folic acid available for fetal growth.
We calculated new birthweight and head circumference centiles for boys and girls between 24 and 42 weeks' gestation from 20,713 singleton live births at our hospital between 1978 and 1984. Among the 803 babies born at or before 34 weeks' gestation, 28% were delivered electively for fetal problems; they were considerably lighter than babies born after spontaneous preterm labour. In contrast, they showed only a small deficit in head circumference, possibly due to a brain sparing effect in growth retarded infants. Electively delivered preterm infants cause a bias in birthweight and head circumference centiles and we recommend that these babies should be excluded when these centiles are calculated.
Neonatal anthropometric charts of the distribution of measurements, mainly birth weight, taken at different gestational ages are widely used by obstetricians and pediatricians. However, the relationship between delivery mode and neonatal anthropometric data has not been investigated in Japan or other countries.
The subjects were selected from the registration database of the Japan Society of Obstetrics and Gynecology (2003–2005). Tenth centile, median, and 90th centile of birth weight by sex, birth order, and delivery mode were observed by gestational age from 22 to 42 weeks among eligible singleton births.
After excluding 248 outliers and 5243 births that did not satisfy the inclusion criteria, 144 980 births were included in the analysis. The distribution of 10th centile curves was skewed toward lower birth weights during the preterm period among both first live births and second and later live births delivered by cesarean section. More than 40% of both male and female live births were delivered by cesarean section at 37 weeks or earlier.
The large proportion of cesarean sections influenced the skewness of the birth weight distribution in the preterm period.
birth weight; distribution; gestational age; cesarean section; preterm
The association between birthweight ratio and outcome was investigated in 429 infants born before 31 weeks' gestation. Birthweight ratio was calculated in each case as birth weight divided by mean birth weight for gestation (from reference data). It was shown that a given ratio corresponded to the same birth centile across the gestational age range studied; a ratio of 0.8 corresponding to the 10th centile. There was a linear relationship between birthweight ratio and requirement for mechanical ventilation and postneonatal mortality. Birthweight ratio was also strongly and linearly related to body weight, length, and head circumference at 18 months' corrected age. Overall, there was no association between this ratio and neurodevelopmental outcome to 18 months. However, the subgroup with the largest weights for gestation (birthweight ratio greater than or equal to 1.1), had significantly higher language subscores than all the other children. Our data show that conventional dichotomous categorisation of preterm infants into small or appropriate for gestation is inadequate when exploring the association between size for gestation and outcome.
To evaluate whether the association between low birthweight and placental abruption is mediated through preterm birth or restricted fetal growth, and if these associations were influenced by maternal thrombophilia status.
Data were derived from the New Jersey-Placental Abruption Study, an ongoing, multicenter, case-control study conducted in New Jersey since August 2002. Abruption cases (n=156) were identified based on a clinical diagnosis, and controls (n=170) were matched to cases based on parity and maternal race. Low birthweight (<2500 g) was stratified based on preterm birth (<37 weeks gestation) and small for gestational age (birthweight <10th centile for gestational age). Maternal thrombophilia assessment was based on serum evaluation (Protein C and S deficiency, activated Protein C resistance ratio, and anticardiolpin antibodies) as well as genetic polymorphisms (methylenetetrahydrofolate reductase, prothrombin gene, and Factor V Leiden). Associations were expressed based on odds ratio (OR) with 95% confidence interval (CI).
Among abruption cases, 60.3% (n=94) were low birthweight in comparison to 11.2% (n=19) of controls (OR 13.7, 95% CI 7.4, 25.2). Furthermore, placental abruption had a significantly increased association with preterm birth in both SGA (OR 17.4, 95% CI 4.6, 64.9) and appropriately grown fetuses (OR 15.8, 95% CI 8.4, 29.8). However, the association between abruption and low birthweight were similar between women with and without thrombophilia.
The association between placental abruption and low birthweight is chiefly mediated through preterm birth, and this association does not appear to be modified by maternal thrombophilia status.
Placental abruption; fetal growth restriction; preterm birth; maternal thrombophilia
Routinely collected data for 187,000 Scottish singleton livebirths in 1980-2 were used to relate the risk of birthweight below 2500 g, 2000 g, 1500 g, and 1000 g to sex of infant and nine maternal factors. Maternal height was a major predictor of birthweight below 2500g but was less important in predicting birthweight in the lower intervals. A history of prenatal death and spontaneous abortion was important for all four intervals and was associated with most extreme risks for birthweight below 1000 g. The analysis confirms that the patterns of risk of birthweight below 2500g and 2000 g associated with social class, marital status, and maternal age and height found among the women of the 1958 cohort of British births are still applicable in the early 1980s.
Birthweight, and head circumference and body weight at preschool age were studied in a group of 212 children exposed to maternal rubella infection. Birthweights were compared to standards for birthweights of British children according to gestational age and birth rank. Children with detectable rubella antibody at the time of the examination were regarded as seropositive and those with no detectable antibody as seronegative. It was shown that the mean birthweight of seronegative and seropositive children without rubella defects did not differ significantly from the 50th centile or from each other, but that those who were seropositive with defects had significantly lower birthweights. Head circumference and body weight were similarly compared to current British standards. Head circumference at follow-up was normal in seronegative and seropositive children without defects, but significantly low in seropositive children with defects, even if retinopathy was the sole defect. The findings for body weight at follow-up were similar, reflecting absence of catch-up growth in weight in the children with congenital rubella defects.
This study has shown that intrauterine growth retardation does not present as the sole manifestation of maldevelopment in congenital rubella.
Although heart rate and respiratory rate are routinely measured in children in acute settings, current reference ranges are not evidence-based. The aim of this study is to derive new centile charts for heart rate and respiratory rate using systematic review data from existing studies, and to compare these with existing international ranges.
We searched MEDLINE, EMBASE, and CINAHL to April 2009, and reference lists to identify studies which had measured heart rate and/or respiratory rate in normal children between birth and 18 years of age. We used a non-parametric kernel regression method to create centile charts for heart rate and respiratory rate with respect to age. We compared existing reference ranges with those derived from the centile charts.
We included 69 studies, 59 of which provided data on the heart rate of 143,346 children, and 20 on the respiratory rate of 3,881 children. Our new centile charts demonstrate the decline in respiratory rate from birth to early adolescence, with the steepest decline apparent in infants under two years; decreasing from a median of 44 breaths/minutes at birth to 26 breaths/minute at the age of two. The heart rate centile chart demonstrates a small peak at one month of age. The median heart rate increases from 127 beats/minute at birth to a maximum of 145 beats/minute at approximately one month of age, before decreasing to 113 beats/minute by the age of two. Comparison of the centile charts with existing published reference ranges for heart rate and respiratory rate show marked disagreement with the centile charts, with limits from published ranges frequently exceeding the 99th and 1st centiles, or crossing the median.
Our review shows that existing international guidelines for heart rate and respiratory rate in children are not based on evidence. We have created new centile charts based on a systematic review of studies which have measured these vital signs in normal children. Clinical and resuscitation guidelines should be updated in the light of these evidence-based reference ranges.
Research funded by the National Institute for Health Research programme grant for applied research ‘Development and implementation of new diagnostic processes and technologies in primary care’. SF was funded by the Engineering and Physical Sciences Research Council and the National Institute for Health Research Biomedical Research Centre Programme.
children; heart rate; respiratory rate; normal; centiles; ranges
Birthweight and gestational age are associated with socioeconomic deprivation, but the evidence in relation to temporal changes in these associations is sparse. We investigated changes in the associations between socioeconomic status (SES) and birthweight and gestational age in Newcastle upon Tyne, North of England, during 1961–2000.
We used population-based data from hospital neonatal records on all singleton births to mothers resident in Newcastle (births with complete covariate information n = 113,182). We used linear regression to analyse the associations between neighbourhood SES and birthweight over the entire 40-year period and by decade, and logistic regression for associations with low birthweight (LBW) and preterm birth, adjusting for potential confounders.
There was a significant interaction between SES and decade of birth for birthweight (p = 0.028) and preterm birth (p < 0.001). Socioeconomic gradients were similar in each decade for birthweight outcomes, but for preterm birth, socioeconomic disparities were more evident in the later decades [for 1961–70, odds ratio (OR) was 1.1, 95% CI 0.9, 1.3, for the most deprived versus the least deprived quartile, while for 1991–2000, the corresponding OR was 1.5, 95% CI 1.3, 1.7]. In each decade, there was a significant decrease in birthweight adjusted for gestational age for the most deprived compared to the least deprived SES group [1961–1970: –113.4 g (95% CI–133.0, –93.8); 1991–2000: –97.5 g (95% CI–113.0, –82.0)], while there was a significant increase in birthweight in each SES group over time.
Socioeconomic inequalities did not narrow over the four decades for birthweight and widened for preterm birth. Mean birthweight adjusted for gestational age increased in all socioeconomic groups, suggesting an overall increase in fetal growth.
Low birthweight; Preterm birth; Socioeconomic status; Townsend deprivation score; Temporal trends
Symphysis-fundus charts were introduced into 50 general practitioner antenatal clinics and the hospital antenatal clinics of two obstetricians in Gloucestershire in February 1985 for a 12-month period. Of the 1139 charts analysed, the sensitivity of one or more low fundal height measurements in predicting birthweight below the tenth centile for gestational age was 51% with a specificity of 88%. In the 319 charts with four or more measurements after 26 weeks gestation a sensitivity of 65% was recorded in predicting birthweight below the tenth centile, rising to 91% in the prediction of birthweight below the fifth centile; the specificity was correspondingly 81% and 80%. The sensitivity of the test varied inversely with maternal body mass index. The mean absolute difference in pairs of observations between general practitioners, midwives and an observer was 1.5 cm. Measurement of symphysis-fundus distance is not a precise diagnostic tool but it does provide an improvement on abdominal palpation in the prediction of small-for-dates infants. The findings of this study support the use of serial symphysis-fundus measurements in community antenatal clinics. Referral for ultrasound investigation is recommended when the measurement is low.
The decision to adopt the new WHO standard in the UK necessitated substantial changes to the neonatal section of the chart, including separation of the preterm UK birthweight reference from the WHO standard. The evidence-based design process has led to several novel features that could be generally applied in other chart designs, and revealed uncertainties leading to inconsistencies in charting. Failing to plot birthweight of term infants at age 0 can lead to spurious centile crossing in the early weeks of life, particularly among infants at the extreme of gestation. Users will need training to use the charts, but this should improve overall understanding and use of charts.
STUDY OBJECTIVE--The aim was to examine the effect of maternal age, gravidity, marital status, previous perinatal deaths, and parental social class on babies born low birthweight, preterm, and small for gestational age. DESIGN--The study used data on discharge summaries from all maternity hospitals in Scotland. SETTING--The study was based on all singleton deliveries in Scotland. PARTICIPANTS--The analysis involved information on 259,462 singleton babies born during the four years 1981-84 in Scotland. MEASUREMENTS AND MAIN RESULTS--Previous perinatal death was found to be the strongest predictor for both preterm and low birthweight. Single mothers were at particularly high risk of having a small for gestational age baby and those who were previously married of having a preterm baby. Women aged less than 20 years old, those over 34 years old, nulligravidae, and those of parity 3 or more were also at increased risk of adverse pregnancy outcome. Mothers and fathers in manual social classes and those who could not be assigned a social class on the basis of their occupation were at increased risk for all three adverse outcomes studied. The babies of parents who were in manual occupations were twice as likely as those of parents in non-manual occupations to be small for gestational age and almost twice as likely to be low birthweight. CONCLUSIONS--Mother's social class is a risk factor for adverse pregnancy outcome independent of maternal age, parity, and adverse reproductive history, and also independent of father's social class. Information on both parents' occupations should be collected in maternity discharge systems.
This study was undertaken to provide reliable up to date information on birth weights and occipitofrontal head circumference measurements in relation to gestational age for English newborn twins. Records from 36 maternity units in England, mainly from 1988-92, have provided data on birth weights for over 19,000 newborn twins with gestational ages ranging from 23 to 41 weeks, and on head circumference measurements for over 5300 twins ranging from 28 weeks to 40 weeks' gestation. Centile charts have been produced for boy and girl twins showing the distribution of these values against gestational age. The findings confirm the greater weights of boys compared with girls throughout, increasing from a mean of about 50 g at early stages to 100 g later, in a similar way to that reported for singletons. Twins were lighter than comparable singletons by about 100 g at 24 weeks, increasing progressively to 4-500 g at 38 weeks' gestation. In contrast, differences in occipitofrontal head circumferences between singletons and twins were only evident with gestations longer than 35 weeks--and from 37 weeks' gestation onwards the mean head circumference of singletons exceeded that of twins by about 5 mm. It is recommended that in evaluating the significance of the birth weight of a twin in relation to gestation, twin standards such as the ones presented here should be used rather than those relating to singletons.
We have studied changes in the birthweight of Asian babies born alive at this hospital between 1968 and 1978. In 1978 Pakistani babies were 139 g heavier but Indian babies only 25 g heavier than 10 years earlier. Contributing to these changes were significantly fewer short mothers and primiparae among Pakistanis, and non-significant increases in gestational age and intrauterine growth (that is, weight centile after allowing for gestational age, parity, and maternal height). Among Indians there were significant increases in maternal height and gestational age, but parity was reduced and intrauterine growth did not increase. In both groups there were fewer teenage mothers, but whereas among Pakinstanis birth intervals of less than one year were less common, there was no such reduction among Indian mothers. The secular change suggests that genetic factors are unlikely to be the major reason why Pakistani babies born in Birmingham are lighter than European babies, and that environmental factors play an important role. Efforts to increase birthweight need to consider both the mothers' physical environment during pregnancy and prepregnancy factors influencing growth in childhood, age at first pregnancy, and birth interval. The study shows a need to describe an 'Asian' population with details of their sub-ethnic structure. The sub-ethnic and secular differences further suggest that a single 'Asian' standard for birthweight and intrauterine growth may be inappropriate; the use of international reference data with which all infants may be compared is preferable.
Objective To assess the main risk factors associated with stillbirth in a multiethnic English maternity population.
Design Cohort study.
Setting National Health Service region in England.
Population 92 218 normally formed singletons including 389 stillbirths from 24 weeks of gestation, delivered during 2009-11.
Main outcome measure Risk of stillbirth.
Results Multivariable analysis identified a significant risk of stillbirth for parity (para 0 and para ≥3), ethnicity (African, African-Caribbean, Indian, and Pakistani), maternal obesity (body mass index ≥30), smoking, pre-existing diabetes, and history of mental health problems, antepartum haemorrhage, and fetal growth restriction (birth weight below 10th customised birthweight centile). As potentially modifiable risk factors, maternal obesity, smoking in pregnancy, and fetal growth restriction together accounted for 56.1% of the stillbirths. Presence of fetal growth restriction constituted the highest risk, and this applied to pregnancies where mothers did not smoke (adjusted relative risk 7.8, 95% confidence interval 6.6 to 10.9), did smoke (5.7, 3.6 to 10.9), and were exposed to passive smoke only (10.0, 6.6 to 15.8). Fetal growth restriction also had the largest population attributable risk for stillbirth and was fivefold greater if it was not detected antenatally than when it was (32.0% v 6.2%). In total, 195 of the 389 stillbirths in this cohort had fetal growth restriction, but in 160 (82%) it had not been detected antenatally. Antenatal recognition of fetal growth restriction resulted in delivery 10 days earlier than when it was not detected: median 270 (interquartile range 261-279) days v 280 (interquartile range 273-287) days. The overall stillbirth rate (per 1000 births) was 4.2, but only 2.4 in pregnancies without fetal growth restriction, increasing to 9.7 with antenatally detected fetal growth restriction and 19.8 when it was not detected.
Conclusion Most normally formed singleton stillbirths are potentially avoidable. The single largest risk factor is unrecognised fetal growth restriction, and preventive strategies need to focus on improving antenatal detection.
There is conflicting evidence about the effect of parental consanguinity on fetal growth. Previous studies have not always allowed for other factors that are known to affect birth weight, in particular, gestational age, parity, and maternal height. We have therefore studied this question in the Pakistani Moslem population in Birmingham. Babies born to parents who were first cousins were on average 80 g lighter than those born to unrelated parents, but this difference was not significant for the size of the sample studied. Nor were there any differences in the other measurements of the babies. After expressing birth weight in terms of centiles for gestational age, sex, parity, and maternal height, however, while there was no difference in the overall distribution of centiles, there were more poorly grown babies--that is, weight below the 10th centile--in the first cousin group. We conclude that parental consanguinity is associated with an increase in the number of poorly grown babies but that the overall effect on mean birth weight is small.
To examine the association between narrowly defined subsets of maternal ethnicity and birth outcomes.
Analysis of 1995-2003 New York City birth certificates linked to hospital discharge data for 949,210 singleton births to examine the multivariable associations between maternal ethnicity and preterm birth, subsets of spontaneous and medically indicated preterm birth, term small for gestational age (SGA), and term birthweight.
Compared to non-Hispanic whites, Puerto Ricans had an elevated odds ratio (OR 1.9, 95% CI 1.9-2.0) for delivering at 32-36 weeks (adjusted for nativity, maternal age, parity, education, tobacco use, pre-pregnancy weight, birth year). We found an excess of adverse outcomes among most Latino groups. Outcomes also varied within regions, with North African infants nearly 100g (adjusted) heavier than sub-Saharan Africans.
The considerable heterogeneity in risk of adverse perinatal outcomes is obscured in broad categorizations of maternal race/ethnicity, and may help to formulate etiologic hypotheses.
Ethnic groups; Epidemiology; Outcomes; pregnancy
The UK 1990 height charts are derived from an up to date dataset and introduce a change in the centile lines, particularly the addition of the 0.4th centile. This study examined the likely impact of these changes. Height data from London school children (1990-1993) were examined using Tanner and Whitehouse (TW) and UK 1990 charts. Numbers of children with height below TW 3rd centile were compared with numbers below the UK 1990 3rd and 0.4th centiles. The TW charts identified only 1% of children below the TW 3rd centile, while the UK 1990 charts identified 3% below the 3rd and 0.4% below the 0.4th centiles. If the 3rd centile remains as the referral 'cut off' for short stature, the introduction of the UK 1990 charts would increase current workload two- to three-fold, while a change to the 0.4th centile would reduce it by 50%. A significant number of children with abnormalities may be excluded from further assessment as a result of this latter change. In this small scale community study it is not possible to assess the consequences of this change. The heights at diagnosis of children with growth hormone (GH) deficiency (peak GH < 20 mU/l during a standard provocation test) were therefore compared to the 0.4th centile (UK 1990 charts). Sixty eight children with heights < 2nd centile (UK 1990 charts) currently receiving GH replacement (17 female, 51 male, aged 9.7, SD 3.5, years) were assessed, and of these, 28 (41%) had heights at diagnosis between 0.4th and 2nd centile, with a mean height standard deviation score of -2.32 (SD 0.21). This suggests that if the 0.4th centile were to be used as the sole criterion for referral for slow growth, a significant proportion of children with abnormality would not be referred for further assessment. The UK 1990 2nd centile should replace the TW 3rd centile. Children below this should undergo an intermediary medical assessment to confirm height measurement, to exclude from referral children with mild familial short stature and to identify concerns regarding the child.
An examination of the recent decline in perinatal mortality in Scotland during the 1970s showed that despite substantial changes in fertility and the demographic pattern of births, differences in the age, parity, and social class composition of the obstetric population in this decade accounted for just 7% of the overall improvement in perinatal mortality between 1970 and 1979. The general pattern of relative risks associated with maternal age, parity, and social class remained largely unchanged. Marginal changes in the birthweight distribution, however, were sufficient to account for 13% of the reduction in perinatal mortality. The low birthweight infant, especially those weighing under 1500 g, assumed increasing importance as a factor in perinatal mortality owing to a progressive worsening in the relative risk of perinatal mortality associated with low birth weight. Although regional differences in perinatal mortality persisted over this period, there occurred some lessening of the traditional inequality between western and eastern parts of the country. Finally, registered causes of perinatal mortality are reviewed. In the absence of other explanations the results of this analysis, collectively, suggest that much of the recent decline in perinatal mortality was perhaps due to changes in obstetric practice and in the clinical management of neonatal morbidity.
Metabolic syndrome has been called a “small baby syndrome,” but other analyses suggest that postnatal growth is more important than birthweight, or that large babies are also at risk. The aim of this analysis was to examine whether there was a relationship between both low and high birthweight and metabolic syndrome, using multiple definitions of metabolic syndrome, and to determine whether this relationship varied by body size across the life course.
Data from the Bogalusa Heart Study, a study of cardiovascular disease in children and young adults, were linked to birth certificate data. Metabolic syndrome was defined by the National Cholesterol Education Program, the International Diabetes Foundation, and the World Health Organization (WHO) definition. Small-for-gestational-age (SGA) was defined as birthweight <10th percentile by sex for gestational age and large-for-gestational-age (LGA) as birthweight >90th percentile. Birthweight-for-gestational-age was also examined as a continuous predictor. Chi-squared tests and logistic regression were used to examine the relationship between birth size and metabolic syndrome.
Higher birthweight-for-gestational-age was associated with a reduced risk of metabolic syndrome, especially by the WHO definition. After adjustment for body mass index (BMI), categorized birthweight was associated with metabolic syndrome, with the protective associations with LGA being stronger than the positive associations with SGA. Among the individual components of metabolic syndrome, higher waist circumference was associated with both SGA and LGA after BMI was controlled for. Effects of SGA and BMI at any age were largely independent rather than interactive.
SGA is associated with some, but not all, components of metabolic syndrome. The relationship between SGA and metabolic syndrome is partially confounded by later BMI.
Background Increases in pre-term births and improved survival rates have led to interest in the association between gestational age and health in adulthood. Associations between gestational age and risk factors for cardiovascular disease have not been fully investigated.
Methods Using data from the 1958 British birth cohort (7847 singletons), the associations between gestational age and blood pressure, glycosylated haemoglobin (HbA1c), lipid levels and body mass index (BMI) at age 44–45 years were examined.
Results After adjustment for sex, birthweight standardized for gestational age and sex and current BMI there was a reduction in systolic blood pressure of 0.53 mmHg (95% CI: 0.32, 0.75) for every 1 week increase in gestational age. There was a non-linear association between gestational age and diastolic blood pressure, with those cohort members born at earlier gestational ages found to have higher diastolic blood pressure than those born at term. These associations remained after adjustments. A ‘U’-shaped association was found between gestational age and BMI among women (P = 0.02 for sex × gestational age interaction) which attenuated after adjustment. There was also a weak inverse association between gestational age and total cholesterol specific to women (P = 0.01 for sex × gestational age interaction). No clear associations were found between gestational age and BMI or total cholesterol in men, or between gestational age and HbA1c or other lipid levels in either sex.
Conclusions In the 1958 British birth cohort duration of gestation was associated with blood pressure in mid-life. Understanding this association is necessary to inform policy and preventative interventions.
Gestational age; lipids; blood pressure; HbA1c; BMI
Babies with low birthweight (<2500 g) are at increased risk of early mortality. However, low birthweight includes babies born preterm and with fetal growth restriction, and not all these infants have a birthweight less than 2500 g. We estimated the neonatal and infant mortality associated with these two characteristics in low-income and middle-income countries.
For this pooled analysis, we searched all available studies and identified 20 cohorts (providing data for 2 015 019 livebirths) from Asia, Africa, and Latin America that recorded data for birthweight, gestational age, and vital statistics through 28 days of life. Study dates ranged from 1982 through to 2010. We calculated relative risks (RR) and risk differences (RD) for mortality associated with preterm birth (<32 weeks, 32 weeks to <34 weeks, 34 weeks to <37 weeks), small-for-gestational-age (SGA; babies with birthweight in the lowest third percentile and between the third and tenth percentile of a US reference population), and preterm and SGA combinations.
Pooled overall RRs for preterm were 6·82 (95% CI 3·56–13·07) for neonatal mortality and 2·50 (1·48–4·22) for post-neonatal mortality. Pooled RRs for babies who were SGA (with birthweight in the lowest tenth percentile of the reference population) were 1·83 (95% CI 1·34–2·50) for neonatal mortality and 1·90 (1·32–2·73) for post-neonatal mortality. The neonatal mortality risk of babies who were both preterm and SGA was higher than that of babies with either characteristic alone (15·42; 9·11–26·12).
Many babies in low-income and middle-income countries are SGA. Preterm birth affects a smaller number of neonates than does SGA, but is associated with a higher mortality risk. The mortality risks associated with both characteristics extend beyond the neonatal period. Differentiation of the burden and risk of babies born preterm and SGA rather than with low birthweight could guide prevention and management strategies to speed progress towards Millennium Development Goal 4—the reduction of child mortality.
Bill & Melinda Gates Foundation.
To describe birth weight and postnatal weight gain in a contemporaneous population of babies born <32 weeks’ gestation, using routinely captured electronic clinical data.
Anonymised longitudinal weight data from 2006 to 2011.
National Health Service neonatal units in England.
Birth weight centiles were constructed using the LMS method, and longitudinal weight gain was summarised as mean growth curves for each week of gestation until discharge, using SITAR (Superimposition by Translation and Rotation) growth curve analysis.
Data on 103 194 weights of 5009 babies born from 22–31 weeks’ gestation were received from 40 neonatal units. At birth, girls weighed 6.6% (SE 0.4%) less than boys (p<0.0001). For babies born at 31 weeks’ gestation, weight fell after birth by an average of 258 g, with the nadir on the 8th postnatal day. The rate of weight gain then increased to a maximum of 28.4 g/d or 16.0 g/kg/d after 3 weeks. Conversely for babies of 22 to 28 weeks’ gestation, there was on average no weight loss after birth. At all gestations, babies tended to cross weight centiles downwards for at least 2 weeks.
In very preterm infants, mean weight crosses centiles downwards by at least two centile channel widths. Postnatal weight loss is generally absent in those born before 29 weeks, but marked in those born later. Assigning an infant's target centile at birth is potentially harmful as it requires rapid weight gain and should only be done once weight gain has stabilised. The use of electronic data reflects contemporary medical management.
Growth; Data Collection; Neonatology; Statistics