Individual efficacy of intermittent preventive treatment with sulfadoxine-pyrimethamine in primi- and secundigravidae in rural Burkina Faso: impact on parasitaemia, anaemia and birth weight

To assess the efficacy at individual level of intermittent preventive treatment with sulfadoxine-pyrimethamine (IPTp-SP) in primi- and secundigravidae in rural Burkina Faso. Data of 1441 women enrolled in a health centre randomized trial and delivering a live-singleton between September 2004 and October 2006 were analysed at individual level. Prevalence of peripheral and placental parasitaemia, anaemia (PCV < 33%), low-birth weight (< 2500 g; LBW), mean packed cell volume (PCV) and birth weight were compared in relation to the number of directly observed SP doses. Two or more doses of SP significantly reduced the risk of placental parasitaemia [adjusted odds ratio (AOR) = 0.04, 95%CI = 0.003-0.60, P = 0.023] and anaemia at delivery (AOR = 0.31, 95%CI = 0.18-0.52, P < 0.001). IPTp was associated with reduced risk of LBW in primigravidae (AOR = 0.11, 95%CI = 0.07-0.17, P < 0.001) but not secundigravidae (AOR = 0.70, 95%CI = 0.26-1.91, P = 0.452). For each increment in number of SP doses mean PCV increased by 1.0% (95%CI = 0.4-1.7, P = 0.005) at 32 weeks gestation, by 1.2% (95%CI = 0.2-2.2, P = 0.025) at delivery and mean birth weight by 220 g (95%CI = 134-306 P < 0.001) in primigravidae and by 102 g (95%CI = 55-148, P = 0.001) in secundigravidae. The risk of malaria infection was significantly reduced by IPTp with SP in primi- and secundigravidae in rural Burkina Faso. The impact on clinical outcomes is lower and mainly limited to primigravidae for LBW. Incomplete uptake of IPTp-SP and limited effect in low risk groups together may substantially dilute the measurable impact of effective interventions. This needs to be taken into account when evaluating interventions at community level.