Spontaneous Postpartum Clearance of Plasmodium falciparum Parasitemia in Pregnant Women, Benin

Abstract

In malaria-endemic areas, pregnant women are more likely to be infected with malaria than non-pregnant women.1 Recent studies have demonstrated that this propensity for malaria to develop during pregnancy is attributed, at least in part, to expression of Plasmodium falciparum peculiar variant antigen on the membrane of the infected erythrocyte, which enables its adherence to specific placental receptors. The accumulation of parasites in the placenta may contribute to low birth weight and maternal anemia, 2 particularly in primigravidae who have not acquired specific immunity to those variant parasites. 3Although the effects of malaria in pregnancy are well documented, little is known about malaria in the postpartum period. A study published in the 1980s showed that women who were parasitemic at delivery cleared their parasitemia spontaneously within 48 hours postpartum. 4 Recently, two longitudinal studies found that women remained at high risk for malaria in the early postpartum period, as during pregnancy.1, 5 To investigate this issue, which may have important consequences for the management of women who recently delivered a child, we studied the immediate postpartum spontaneous evolution of malaria infections at delivery in pregnant women in Benin.Data were collected during a clinical trial on intermittent preventive treatment in pregnancy (IPTp), which was conducted during July 2005-April 2008 in Benin. 6 The study protocol was described elsewhere 6 and was reviewed and approved by ethics committees in France and Benin.Briefly, pregnant women were randomized to receive two doses of IPTp with either sulfadoxine-pyrimethamine or mefloquine. At delivery, malaria thick blood smears were prepared from maternal peripheral blood and from the maternal side of the placenta. All women who had a positive peripheral thick blood smear at delivery were tested for parasitemia 24 hours later and then daily until no parasites were detected. Control blood smears were prepared at the hospital before discharge or during scheduled visits at home. For logistical reasons, in selected cases, blood smears were not prepared on day 1 after delivery, but on days 2-5. If these women had symptoms of malaria at delivery or during follow-up or if there was a doubt on their likeliness to attend the maternity clinic in case of clinical signs (e.g., women living in remote areas), they were given a 7-day quinine treatment.During a six-week period after delivery, all women were encouraged to attend the study maternity clinic if they had symptoms suggestive of malaria. On this occasion, a thick blood smear was prepared and women were treated if malaria was confirmed. Finally, all women had a scheduled appointment at week 6 after delivery to test for current symptoms suggestive of malaria and history of fever or malaria within the past six weeks.Thick blood smears were considered positive if an asexual stage parasite was detected after examination of 200 microscope fields. Cross-readings were made for all blood smears. In case of discrepancy, a ...

The epidemiology of postpartum malaria: a systematic review

“…In theory, the increased susceptibility during pregnancy normalizes immediately after delivery when the placenta, where the parasites can adhere during pregnancy, is expelled. This is supported by the reports of spontaneous clearance of P. falciparum parasites within 24 hours after delivery in high transmission areas in Africa[ 8 , 9 ]. In contrast, in Malawi[ 10 ] among women of which some were screened at day 0, others at day 1, 2, until 1 week after delivery, the proportion with a positive malaria blood smear was constant each day over the first seven days (K. Msyamboza, personal communication).…”

The case for PfEMP1-based vaccines to protect pregnant women againstPlasmodium falciparummalaria

“…Apart from this putative indirect role, it is repeatedly suggested that parasites not expressing VAR2CSA and sequestering in organs other than the placenta also play a direct and important role in malaria in pregnancy [26,77]. Although peripheral blood P. falciparum parasitemia in pregnant women living in stable parasite transmission areas often seems to be derived from a parasite population with a placental sequestration focus [23, [78][79][80], such a population may also be just one of several populations present in the peripheral blood [12,23,79]. These populations can be clonally different from each other [81] or genotypically identical subpopulations expressing different PfEMP1 proteins and with different tissue tropisms.…”

Malaria in the Post-Partum Period; a Prospective Cohort Study

“…Less is known about susceptibility in the post-partum period. Some studies report prolonged and increased susceptibility to malaria comparable to that in pregnancy[2], [3], while others report spontaneous clearance of P.falciparum parasites within 24 hours of delivery[4], [5]. A recent review including 11 studies suggests a transition phase after delivery in which the susceptibility gradually returns to pre-pregnancy levels[6].…”