The Effect of Malaria During Pregnancy on Infant Susceptibility to Malaria

Background: Malaria during pregnancy threatens the health of mothers and newborns and may have long-lasting consequences on infant health. Observational studies suggest that placental malaria may be associated with increased risk of malaria in the infant. However, previous studies are limited by the inability to control for shared exposures and failure to detect episodes of malaria that occurred prior to delivery. We hypothesize that placental malaria will be associated with the highest risk of malaria during infancy and that maternal peripheral malaria in the absence of placental infection will be protective.

Methods: We conducted a randomized clinical trial that of three chemo-prevention strategies during pregnancy, resulting in three distinct malaria exposure groups: placental malaria; peripheral malaria without placental infection; and no malaria during pregnancy. We are following infants born to mothers in the clinical trial through active and passive molecular surveillance for malaria.

Results: 463 infants born to mothers in the clinical trial have been followed for a median duration of 251 days after birth. 333 infants were born to mothers with no evidence of malaria during pregnancy, 75 to mothers with placental malaria and 55 to mothers with only peripheral infection. Malaria infection during the first year of life was detected in 10.0%, 26.3% and 16.7% of those born to mothers with no malaria, placental malaria and peripheral malaria, respectively. The cumulative incidence of malaria per person year was highest among infants born to mothers with placental malaria, 0.32 compared to 0.17 and 0.19 per person year of follow up among infants born to mother with no malaria and peripheral malaria respectively. The difference did not achieve statistical significance (p=0.12). Follow up is underway to collect more data from the infants as they get older and experience more malaria episodes.

Conclusion: Malaria infections are frequent in infancy. There is preliminary evidence that exposure to placental malaria infection may increase the infant’s risk of malaria. Results of this study will inform the design and implementation of innovative and highly effective prenatal interventions to protect the health of pregnant women, newborns and infants from malaria.