Risk factors for fetal anaemia in a malarious area of Malawi.

The prevalence of infants born with low cord haemoglobin (fetal anaemia) is high in areas where malaria and iron deficiency anaemia in pregnancy are common. The objective of the present study was to determine risk factors for fetal anaemia in an area of high malaria transmission in southern Malawi. A case control study was undertaken with fetal anaemia defined as cord haemoglobin (Hb) < 12.5 g/dl. Between March 1993 and July 1994, pregnant women attending the study hospitals for the first time in that pregnancy were enrolled. Data on socio-economic status, anthropometry, previous obstetric history and current pregnancy were collected. Malaria parasitaemia, Hb levels and iron status were measured in maternal blood at recruitment and delivery and in umbilical venous blood. Fetal anaemia occurred in 23.4% of babies. Mean (SD) cord Hb was 13.6 g/dl (1.83). Factors associated with fetal anaemia were: birth in the rainy season [adjusted odds ratio (AOR) 2.33, 95% CI 1.73-3.14], pre-term delivery (AOR 1.60, 1.03-2.49), infant Hb < 14 g/dl at 24 hours (AOR 2.35, 1.20-4.59), maternal Hb at delivery < 8 g/dl (AOR 1.61, 1.10-2.42) or <11 g/dl (AOR 1.60, 1.10-2.31). A higher prevalence of fetal anaemia occurred with increasing peripheral Plasmodium falciparum parasite density (p=0.03) and geometric mean placental parasite densities were higher in babies with fetal anaemia than in those without (3331 vs 2152 parasites/microl, p=0.07). Interventions should aim to reduce fetal anaemia by improving malaria and anaemia control in pregnancy and by addressing the determinants of pre-term delivery.