In the Absence of Syphilis, Anemia Causes the Majority of Stillbirths in Tanzania
In a sample of pregnant Tanzanian women including both women who had been screened and treated for syphilis and a control group of uninfected women, 3% experienced a stillbirth, and 4–12% of those having live births delivered prematurely or delivered infants with a low birth weight or intrauterine growth retardation.1 Maternal factors associated with elevated risks of one or more of these adverse birth outcomes included shorter stature, untreated bacterial vaginosis, and malaria and anemia, among others. Between 20% and 34% of the adverse birth outcomes were attributable to maternal or placental malaria (or both), and fully 63% of stillbirths were attributable to maternal anemia.
The study, which took place in Mwanza city, had the primary aim of assessing the effectiveness of antenatal screening for and treatment of syphilis. Women visiting the city's main antenatal clinic during 1997–2000 were eligible if they were pregnant with an apparently healthy single fetus, did not have diabetes or hypertension, and had not had vaginal bleeding during their pregnancy. Women with serological evidence of syphilis were recruited; for each of them, two women without syphilis were chosen. They provided information about their social and demographic characteristics, obstetric history and symptoms of reproductive tract infections (RTIs). Blood, vaginal, cervical and urine specimens were collected for RTI testing, and women with positive results were offered 1treatment. In addition, all women were given iron and folate supplements and chloroquine (an antimalarial drug). At delivery, blood was collected to test for HIV and maternal malaria and anemia, and the placenta was examined microscopically for placental malaria. Birth outcomes were recorded at delivery.
At the time of enrollment, the 1,536 women included in main analyses had an average age of about 24 years, and 86% were married. Their mean gestational age was about 25 weeks, and only 18% of women had received antenatal care before 20 weeks. Thirty percent had candidiasis, 30% bacterial vaginosis and 21% trichomoniasis, while smaller proportions had chlamydia (7%) or gonorrhea (2%). At the time of delivery, 65% of women had anemia, and substantial proportions had malarial parasites in their blood (10%) or placenta (39%). In addition, 12% were infected with HIV.
Overall, 18% of women had an adverse birth outcome. For 3%, pregnancy ended in stillbirth (fetal death after 22 weeks of gestation) or intrauterine fetal death (fetal death at or before 22 weeks of gestation). In multivariate analysis, women shorter than 156 cm in height had elevated odds of these outcomes relative to their taller counterparts (odds ratio, 2.6). In addition, compared with other women, women who had experienced a stillbirth before had a sharply elevated likelihood of these outcomes (7.5), and anemic women had a higher likelihood than their nonanemic peers (3.7).
Among women who had live births, 12% delivered prematurely (before 37 weeks of gestation). Women had elevated odds of this outcome if they were 16 or older at sexual debut than if they were younger (odds ratios, 2.0–2.2). The risk was also higher among women who had untreated bacterial vaginosis than among their uninfected counterparts (2.9), and among women who had malaria in their blood at delivery relative to those who did not (3.2).
Slightly more than 8% of women with live births gave birth to an infant with low birth weight (less than 2,500 g). The odds of this outcome were lower among women of Sukuma ethnicity than among women of other ethnicities (odds ratio, 0.6), among women who worked outside the home than among their counterparts who did not (0.3–0.5) and among women who had treated or untreated chlamydia than among their uninfected counterparts (0.2–0.3). In contrast, women were more likely to deliver an infant with low birth weight if they were shorter (1.8) and markedly more so if they had malaria in their blood at delivery (5.4).
About 4% of women with full-term live births delivered an infant who had intrauterine growth retardation (a low birth weight when born at or after 37 weeks of gestation). Women's odds of this outcome were elevated if they were shorter (odds ratio, 1.9), if their infant was female (2.1) and if they had malaria in their blood at delivery (2.8).
In a final set of analyses, sizable minorities of births with outcomes of prematurity (14%), low birth weight (25%) or intrauterine growth retardation (17%) were attributable to maternal malaria. Between 20% and 34% of the four types of adverse birth outcomes individually could be attributed to malaria (maternal, placental or both), and the value was 22% when these outcomes were combined. In addition, almost two-thirds of stillbirths (63%) and nearly a quarter of all adverse birth outcomes combined (23%) were attributable to maternal anemia. In contrast, the proportions attributable to maternal HIV infection were not significant and amounted to only 0–5%.
Discussing the findings, the researchers note that with the exception of untreated bacterial vaginosis, RTIs—although common—were not risk factors for adverse birth outcomes in a setting where clinicians tested for and treated these infections. In addition, they point out, when RTIs (including syphilis) were treated, anemia and malaria became the predominant preventable causes of such outcomes. They speculate that poor adherence to iron supplementation and resistance to chloroquine may explain why some women in the study still had anemia and malaria (which also contributes to anemia), and they note that more effective antimalarial regimens could have a potentially large benefit for birth outcomes in such populations. "Providing reproductive health services that include treatment of RTIs and prevention of malaria and maternal anaemia to reduce adverse birth outcomes remains a priority," the researchers conclude.—S. London
1. Watson-Jones D et al., Adverse birth outcomes in United Republic of Tanzania—impact and prevention of maternal risk factors, Bulletin of the World Health Organization, 2007, 85(1):9–18.