Consequences of gestational malaria on birth weight: finding the best timeframe for intermittent preventive treatment administration.

To investigate the consequences of intermittent preventive treatment (IPTp) timing on birth weight, we pooled data from two studies conducted in Benin between 2005 and 2010: a prospective cohort of 1037 pregnant women and a randomised trial comparing sulfadoxine-pyrimethamine (SP) to mefloquine in 1601 women. A total of 1439 women (752 in the cohort and 687 in the SP arm of the randomised trial) who delivered live singletons were analysed. We showed that an early intake of the first SP dose (4 months of gestation) was associated with a lower risk of LBW compared to a late intake (6-7 months of gestation) (aOR = 0.5 p = 0.01). We also found a borderline increased risk of placental infection when the first SP dose was administered early in pregnancy (aOR = 1.7 p = 0.1). This study is the first to investigate the timing of SP administration during pregnancy. We clearly demonstrated that women who had an early intake of the first SP dose were less at risk of LBW compared to those who had a late intake. Pregnant women should be encouraged to attend antenatal visits early to get their first SP dose and a third dose of SP could be recommended to cover the whole duration of pregnancy and to avoid late infections of the placenta.