Minimal impact by antenatal subpatent P. falciparum infections on delivery outcomes in Malawian women: a cohort study.

Antenatal malaria screening with a rapid diagnostic test (RDT) and treatment only of RDT-positive women may potentially prevent low birthweight resulting from malaria. The consequences of subpatent antenatal infections below the detection limit of RDTs are incompletely understood. In Malawi, pregnant women of any gravidity were tested at each antenatal visit for P. falciparum using RDT and PCR and followed until delivery. Associations between antenatal infections and delivery outcomes were assessed with Poisson regression or ANOVA. Compared to women with no detected antenatal P. falciparum infections, women with RDT-positive infections delivered babies with lower mean birthweights: 2960 vs 2867 grams[g] (mean difference[MD]: -93g; 95% confidence interval[CI]: -27,-159; p=0.006); this was not observed among women with only subpatent infections (mean: 3013g; MD: +54; 95% CI: -33,+140; p=0.2268). These differences were apparent early in pregnancy: At second trimester enrollment, compared to uninfected women, RDT-positive women delivered babies with lower mean birthweight (MD: -94g; 95% CI: -31,-156; p=0.003), but women with subpatent infections did not (MD: +36g; 95% CI: -49,+122; p=0.409). Subpatent antenatal P. falciparum infections were not associated with adverse delivery outcomes. The association of patent infections at enrollment with low birthweight suggests the importance of early-pregnancy P. falciparum prevention.