Elevated body mass index during pregnancy and gestational weight gain in HIV-infected and HIV-uninfected women in Cape Town, South Africa: association with adverse birth outcomes

Objectives To examine the association between maternal body mass index (BMI) and gestational weight gain (GWG) and adverse birth outcomes in HIV-infected and HIV-uninfected women. Methods In an urban South African community, 2921 consecutive HIV-infected and HIV-uninfected pregnant women attending primary healthcare services were assessed at their first antenatal visit. A subset of HIV-infected women enrolled in a longitudinal study was assessed three times during pregnancy. All women had birth outcome data from medical records and study questionnaires. In analyses, the associations between BMI, GWG, maternal factors and adverse birth outcomes were assessed with logistic regression models. Results The estimated pre-pregnancy BMI median was 29 kg/m(2) (IQR, 24-34) overall, 29 kg/m(2) (IQR, 24-34) for HIV-uninfected and 28 kg/m(2) (IQR, 24-34) for HIV-infected women; HIV prevalence was 38%. In adjusted models, increased BMI in the overall cohort was positively associated with age, haemoglobin and parity at first antenatal visit. Maternal obesity was associated with increased likelihood of having high birthweight (aOR 2.54, 95% CI 1.39-4.66) and large size for gestational age (aOR 1.66, 95% CI 1.20-2.31) infants. In the subset cohort, GWG was associated with increased likelihood of spontaneous preterm delivery (aOR 4.35, 95% CI 1.55-12.21) and high birthweight (aOR 3.00, 95% CI 1.22-7.34) infants. Conclusion Obesity during pregnancy is prevalent in this setting and appears associated with increased risk of adverse birth outcomes in both HIV-infected and HIV-uninfected women. Weight management interventions targeting women of child-bearing age are needed to promote healthy pregnancies and reduce adverse birth outcomes.