Our key finding was that despite the WHO recommendations and the high occurrence of adverse health conditions and birth outcomes, only one fifth of the pregnant women visiting KCMC report using iron or folic acid supplements during pregnancy. Remarkably, women with morbidity were less likely to be prescribed or use folic acid and iron supplements. The proportion of women reporting supplementation with folate and/or iron is lower than what has been found in developed countries. Countries such as the USA, Norway, and the Netherlands report folic acid supplementation among pregnant women at 43%, 35%, and 72.4%, respectively [2
]. Typically, iron supplementation is higher than folic acid supplementation. In the USA and the Netherlands iron supplementation among pregnant women is 72% and 77%, respectively [18
]. In developing countries, iron supplementation during pregnancy is as high as 70% in the Philippines and 69% in Senegal [20
Our finding of decreased supplementation among women with co-morbidities (other than anaemia), also after accounting for number of antenatal visits in the adjusted analyses, contrast with other studies where women with co-morbidities are more likely to use folic acid and iron supplements during pregnancy [16
]. However, these other studies were conducted in developed countries where diagnosis is almost always tied to treatment and where women who are recognized as having co-morbidities during pregnancy tend to receive more intensive antenatal care. This may not be the case in Northern Tanzania where the presence of chronic and infectious diseases could be an indicator of poor access to health care, a factor which also contributes to lower utilization of antenatal care services and thus use of folic acid and iron supplements. This explanation is supported by our findings that women who have more ANC visits have significantly greater odds of using folic acid and both folic acid and iron supplements. Similar results have been found in previous studies [5
The WHO estimates that, globally, 41% of women suffer from anemia as result of iron deficiency resulting from low supplementation [24
]. Provision of folic acid and iron supplements, in addition to a standard weekly dose of prophylactic chloroquine for malaria prophylaxis, dramatically reduced the prevalence of anaemia during pregnancy in a prospective intervention study of 1045 women in two antenatal clinics in Dar Es Salaam [13
]. However, factors associated with intake of these supplements are unclear, and may be setting-specific. In a study from Senegal, iron supplementation adherence was increased in women who were offered free access to supplements compared to women who only received a prescription (86% vs. 49%). Counselling on the health benefits of supplementation significantly increased compliance among the Senegalese [21
]. In our study sample, the proportion receiving supplementation was low despite a very high rate of attendance to antenatal clinics – these clinic visits presumably included counselling. Because folic acid and iron are prescribed and dispensed with a very low co-payment (US$ 0.25 per monthly dose), the low use of supplementation, may be a result of a lack of knowledge about the benefits of supplementation rather than non-availability. Interventions involving educating health care providers and ensuring availability of folic acid and iron have been shown to improve intake, as evidenced by a precipitous decrease in prevalence of anemia during the course of pregnancy in a population where provider-education was given [13
Notably, primiparous women with anaemia during pregnancy were also found to have significantly greater odds of using any supplements than multiparous women. This is a consistent finding in studies that have considered parity as a predictive factor for folic acid and iron supplementation [7
]. The common explanation for finding is that multiparous women may have a more casual attitude to supplementation especially if they have had uncomplicated pregnancies in the past.
The definition of anaemia (haemoglobin less than 8.5
g/dl) in the birth registry corresponds with national criteria which are applied at antenatal clinics for referral and further investigation. However, since prevalence estimates for anaemia usually include all individuals with haemoglobin less than 11
g/dl, which includes less severe anaemia, it is difficult to compare the prevalence seen in our study sample to the prevalence for the whole country [12
]. In a well designed study of 2235 pregnant women in the Dar Es Salaam region, 60% were anaemic and 2.2% severely anaemic at the first booking [13
]. An earlier study investigating haemoglobin concentrations in pregnant women in the Moshi area also showed a high prevalence of anaemia [27
]. The WHO bases its recommendations for folic acid and iron supplementation mostly on data from women with anaemia defined as haemoglobin less than 11
g/dl, and the presence of anaemia, based solely on haemoglobin level, is the main indication for folic acid and iron supplementation [4
]. Although hemoglobin is measured at antenatal visits, supplementation is mainly based on clinical signs of anaemia and not haemoglobin level specifically (personal communication). Increasing supplementation in this region will require antenatal care clinics at KCMC and elsewhere to reconsider their definition of anaemia to make it consistent with the WHO definition and use these criteria for prescribing and dispensing iron and folic acid supplements.
While it is clear that women with HIV will especially benefit from folic acid and iron supplementation [25
], our study showed that women with unknown HIV status were more likely to use both iron and folic acid supplements. For women in Northern Tanzania, and perhaps other developing countries, special attention needs to be paid to providing supplements to women with chronic and infectious diseases prior to and during pregnancy. Only in the case of malaria prophylaxis with sulfadoxine-pyrimethamine should special consideration be given in the administration of folic acid as it reduces the efficacy of sulfadoxine as an antimalarial [26
A major strength of this study is the large sample size. Another strength is the method of data collection through a comprehensive birth registry. The birth registry data were carefully collected and comprise information obtained from questionnaire based interviews done by designated midwives and women’s medical records. The information obtained in the questionnaires was cross checked against patient records.
A limitation of this study is that the coverage of births in the KCMC region in not complete. It is estimated that 29% of births in the KCMC catchment region occur at home [12
]. KCMC is not primarily a referral hospital but also serves as a local hospital for the area, and the ethnic and socio-demographic composition of the women who deliver at KCMC is diverse. However, because of its’ status as a referral hospital, women who deliver at KCMC may represent a somewhat more privileged group than those who deliver at home or at local hospitals in the area. In order to obtain a more population based sample we excluded women who were referred for delivery at KCMC due to complications. A second limitation is the fact that health conditions were based on self-reports with supplementary information from medical records. Some of the medical diagnoses were not established by diagnostic tests and may thus be over or underestimated in this sample. A third limitation of this secondary data analysis is the availability of only dichotomous data for characterizing outcomes, as timing and frequency of use of folic acid or iron supplements was not available.