Malaria in pregnancy: adverse effects on haemoglobin levels and birthweight in primigravidae and multigravidae

BACKGROUND In areas of endemic transmission, malaria in pregnancy is associ ated with severe maternal anaemia and low birthweight babies. The prevalenc e of infection is highest in primigravidae (PG), and hence control efforts are usually geared towards this high risk group. Using a sensitive measure of placental infection, we investigated the relationship between active-acu te, active-chronic and past placental infection with maternal anaemia and l ow birthweight in women of all gravidities. METHODS Between January 1996 and July 1997, 912 women delivering in Kilifi District Hospital, Kenya, were recruited. Haemoglobin and peripheral malari a slides were taken prior to delivery, placental biopsies and smears were t aken at the time of delivery and birthweight and maternal height and weight were measured soon after birth. Information was obtained on socio-economic and educational status. The association between placental malaria, severe anaemia and low birthweight was investigated for women of different gravidi ties. FINDINGS By placental histology, the prevalence of active or past malaria i n all gravidities was high, ranging from 64% in PG to 30% in gravidities 5 and above. In gravidities 1-4, active malaria infection was associated with severe maternal anaemia, adjusted OR 2.21 (95% Cl 1.36, 3.61). There was a significant interaction between chronic or past malaria and severe anaemia in their effects on birthweight, whereby the risk of low birthweight was v ery high in women with both chronic or past placental malaria and severe an aemia: OR 4.53 (1.19, 17.2) in PG; 13.5 (4.57, 40) in gravidities 2-4. INTERPRETATION In this area of moderate malaria transmission, women of all parities have substantially increased risk of low birthweight and severe an aemia as a result of malaria infection in pregnancy. The risk of low birthw eight is likely to be particularly high in areas with a high prevalence of severe anaemia.