Maternal and household risk factors for malaria in pregnancy and low birthweight: a prospective cohort study from Uganda

Background Malaria is a leading cause of illness and death in pregnant women and newborns. In 2023, an estimated 12.4 million pregnant women were infected with malaria parasites, resulting in 351,000 low birth weight deliveries. Maternal and household factors associated with malaria in pregnancy and low birth weight were investigated in a high-transmission area of Uganda. Methods. Data come from a randomized controlled trial of intermittent preventive treatment in pregnancy (IPTp) conducted from December 2020 to July 2024 in Busia District. Maternal and household data were collected using structured questionnaires. Women were followed through delivery including monthly assessment of microscopic parasitemia, assessment of placental malaria by histopathology, and birth weight. Associations between maternal and household factors were assessed: 1) parasitaemia at enrolment, 2) parasitaemia during pregnancy after starting IPTp, 3) high-grade placental malaria, and 4) low birth weight (< 2500gm). Results. Of 2,757 women enrolled, 2,728 (98.9%) had a household survey completed and were included in study. Overall, 38.1% had parasitemia at enrolment, 6.5% had parasitemia following initiation of IPTp, 6.4% had high-grade placental malaria, and 6.8% of live births had low birth weight. Parasitemia at enrolment was more common in those 16–21 years of age (RR = 1.62, 95% CI 1.31–1.99 p < 0.001), primigravida (RR = 1.86, 95% CI 1.57–2.21, p < 0.001)), and living in traditional houses (RR-1.17 95% CI 1.06–1.30, p = 0.002). These associations persisted after IPTp initiation: younger age (RR = 1.72, 95% CI 1.22–2.43, p < 0.002), primigravida (RR = 2.40, 95% CI 1.81–3.20, p < 0.001), and traditional housing (RR = 1.30 95% CI 1.01–1.60, p = 0.02). Maternal level of education was not associated with malaria parasitaemia both at enrollment and after initiation of IPTp. Primigravida was strongly associated with high-grade placental malaria (RR = 4.20, 95% CI 2.33–7.59, p < 0.001)) and low birth weight (RR = 2.14, 95% CI 1.18–3.89, p = 0.01). However, there were no significant associations between maternal age, level of education, household wealth, and household construction with high-grade placental malaria or low birthweight. Conclusions. In an area of high malaria transmission, young primigravida women and those living in traditionally constructed houses had the greatest risk of malaria parasitemia during pregnancy. Primigravida women also had higher risks of low birth weight and high grade placental malaria.