Impact of malaria during pregnancy on low birth weight in sub-Saharan Africa

Abstract

Malaria during pregnancy can result in low birth weight (LBW), an important risk factor for infant mortality. This article reviews the pathological effects of malaria during pregnancy and the implications for the newborn's development and survival. Empirical data from throughout Africa on associations between placental malaria and birth weight outcome, birth weight outcome and infant mortality, and the rates of LBW in areas with various levels of malaria transmission are evaluated to assess the increased risks of LBW and infant mortality associated with malaria. It is estimated that in areas where malaria is endemic, around 19% of infant LBWs are due to malaria and 6% of infant deaths are due to LBW caused by malaria. These estimates imply that around 100,000 infant deaths each year could be due to LBW caused by malaria during pregnancy in areas of malaria endemicity in Africa.

FIG. 1.

Proportions of LBW and normal birth weight (NBW) babies dying in the first month and the first year of life in sub-Saharan Africa. Thick lines represent the medians, boxes represent the interquartile ranges, and I bars represent the ranges of data points. (Reprinted from reference with permission of the publisher.)

FIG. 2.

Number of infant deaths due to malaria during pregnancy in areas of stable malaria risk in sub-Saharan Africa. Population of live births refers to number of live births in areas at risk for stable endemic malaria in 2000, as estimated from maps of malaria risk and population models (74). The infant mortality rate is a summary of the rate for sub-Saharan African in 2001 (85). The percentage of infant deaths was determined by using the formula and data on mortality risks presented by Guyatt and Snow (26) with the following revised probabilities based on the new data in Table 1: 0.257 for placental malaria infection (PI), 0.262 for LBW given placental infection (qLBW; range, 0.228 to 0.309), and 0.137 for LBW given no placental infection (range, 0.117 to 0.147). It is estimated that 5.68% (range, 3.69 to 8.77%) of infant deaths are due to malaria-induced LBW. The percentage of LBW infants in areas of malaria endemicity is 17%, the median of the results of 11 studies presented in Table 1. This figure is supported by the data from 31 studies which reported a malaria risk of >25% (Table 2), with a median LBW of 16.4%. The percentage of LBW infants due to malaria during pregnancy is 19% (range, 14 to 25%), which is the population-attributable fraction from Table 1. The percentage of LBW infants dying in the first year of life is 16.2%, based on the mortality risk of 0.162 in five studies reported by Guyatt and Snow (26).