Plasmodium falciparum infection during pregnancy leads to adverse outcomes including low birthweight. Infection during pregnancy leads to infected erythrocytes sequestering within the placenta which can have severe consequences for both mother and child, not only low birthweight but also maternal anaemia, preterm delivery and foetal death. However, contemporary estimates of the potential burden of malaria in pregnancy in Africa (in the absence of interventions) are poor. In a study published this week in the Journal Lancet Global Health, Head of the Malaria in Pregnancy Consortium, LSTM’s Professor Feiko ter Kuile, is among researchers who have aimed to estimate the need to protect pregnant women from malaria across Africa.
Using a mathematical model applied to estimates of the geographical distribution of P falciparum across Africa in 2010, the team led by Dr Patrick Walker and Professor Azra Ghani from Imperial College London, estimated the number of pregnant women who would have been exposed to infection that year in the absence of pregnancy-specific intervention. They then used estimates of the parity-dependent acquisition of immunity to placental infection and associated risk of low birthweight to estimate the number of women who would have been affected.
Professor ter Kuile, who was second author on the study, said: “The model from Imperial College London estimated that, without pregnancy-specific protection, 12·4 million pregnant women would have been exposed to infection, which accounts for nearly 45% of all 27.6 million livebirths in malaria endemic areas in Africa in 2010. 11·4 million, which is 41·2% of all livebirths, having placental infection. This infection leads to an estimated 900 000 low birthweight deliveries per year. Another important finding was that 65·2% of placental infections were estimated to first occur around the end of the first trimester, when the placenta becomes susceptible to infection.
The calculations in the study represents the first contemporary estimates of the geographical distribution of placental infection and associated low birthweight. The risk of placental infection across Africa in unprotected women is high. Professor ter Kuile continued: “These results suggest the potential importance of reducing exposure to malaria in the early stages of pregnancy, or even immediately before pregnancy, such as by ensuring that women of child bearing age all have access to insecticide-treated nets. Prevention of these early infections are likely to be very effective in reducing the corresponding risk of low birthweight, especially in women during their first pregnancy.”
Estimated risk of placental infection and low birthweight attributable to Plasmodium falciparum malaria in Africa in 2010: a modelling study
Dr Patrick G T Walker PhD,Prof Feiko O ter Kuile PhD,Tini Garske PhD,Clara Menendez PhD,Prof Azra C Ghani PhD
The Lancet Global Health - 1 August 2014 (Vol. 2, Issue 8, Pages e460-e467)
DOI: 10.1016/S2214-109X(14)70256-6