Pregnant women are more susceptible to, and severely affected by, malaria. An estimated 125 million women are at risk of malaria in pregnancy (MiP) every year. Notably, the majority (76%) of women at risk of MiP live outside of Africa, where transmission is low and falciparum and vivax malaria co-exist. To reduce the burden of MiP, the WHO recommends that in areas of moderate to high transmission in Africa, pregnant women should receive intermittent preventive antimalarial treatments. Outside of Africa, there are no formal guidelines for the control and prevention of MiP.
Using data from 49,796 pregnancies (16% (7957) of women exposed to malaria during pregnancy), we assessed the association between the gestational age at first antenatal consultation (i.e. when women started routine screening) and birthweight-for-gestational age. Then, amongst women who had malaria detected after their first antenatal consultation, we assessed the association between days absent from screening prior to initial malaria detection and birthweight-for-gestational age.
The study population were women attending antenatal clinics on the Thai-Myanmar border, between 1986 and 2015. Here pregnant women are followed prospectively from first antenatal visit, returning weekly or fortnightly for malaria screening, until delivery.
Delayed presentation to antenatal care was moderately associated with reduced birthweight-for-gestational age in women with MiP (especially for women with falciparum malaria), but not in women with no MiP. In women with MiP detected subsequent to screening initiation, longer absences from screening were associated with modest reductions in birthweight-for-gestational age. This was particularly evident for falciparum MiP detected in third trimester, whereby a 6-week absence was associated with clinically significant reductions in birthweight-for-gestational age.
Our findings demonstrate that MiP interventions should be started as early as possible during pregnancy, and preconception interventions for women of reproductive age should be considered to eliminate MiP and its adverse consequences.