Maternal HIV infection associated with small-for-gestational age infants but not preterm births: evidence from rural South Africa

BACKGROUND Human immunodeficiency virus (HIV) is prevalent in many countries where small-for-gestational age (SGA) and premature delivery are also common. However, the associations between maternal HIV, preterm delivery and SGA infants remain unclear. We estimate the prevalence of SGA and preterm (<37 weeks) births, their associations with antenatal maternal HIV infection and their contribution to infant mortality, in a high HIV prevalent, rural area in South Africa. METHODS Data were collected, in a non-randomized intervention cohort study, on all women attending antenatal clinics (2001-2004), before the availability of antiretroviral treatment. Newborns were weighed and gestational age was determined (based on last menstrual period plus midwife assessment antenatally). Poisson regression with robust variance assessed risk factors for preterm and SGA birth, while Cox regression assessed infant mortality and associated factors. RESULTS Of 2368 live born singletons, 16.6% were SGA and 21.4% were preterm. HIV-infected women (n= 1189) more commonly had SGA infants than uninfected women (18.1 versus 15.1%; P = 0.051), but percentages preterm were similar (21.8 versus 20.9%; P = 0.621). After adjustment for water source, delivery place, parity and maternal height, the SGA risk in HIV-infected women was higher [adjusted relative risk (aRR) 1.28, 95% confidence interval (CI): 1.06-1.53], but the association between maternal HIV infection and preterm delivery remained weak and not significant (aRR: 1.07, 95% CI: 0.91-1.26). In multivariable analyses, mortality under 1 year of age was significantly higher in SGA and severely SGA than in appropriate-for-gestational-age infants [adjusted hazard ratio (aHR): 2.12, 95% CI: 1.18-3.81 and 2.77, 95% CI: 1.56-4.91], but no difference in infant mortality was observed between the preterm and term infants (aHR: 1.18 95% CI: 0.79-1.79 for 34-36 weeks and 1.31, 95% CI: 0.58-2.94 for <34 weeks). CONCLUSIONS Maternal HIV infection increases the risk of SGA, but not preterm births, in this cohort.