96 Uneke: Effects of placental malaria on perinatal outcome of congenital malaria. Although previously thought to be a rarity in sub-Saharan Africa, a recent review has indicated that congenital malaria is more common than previously thought [12]. While still debatable, congenital malaria may be defined as the presence of asexual stages of P. falciparum in cord blood smear at delivery or in peripheral blood smear of the infant in the first seven days of life, ir- respective of clinical symptoms [12]. Nor- mally, symptoms occur 10 to 30 days postpartum; however, the disease may be seen in a day-old infant or appear after weeks to months [6]. Interestingly, earlier reports from sub-Saharan Africa rarely identified clinical disease as a consequence of congen- itally acquired malaria, and only a few reports before the 1970s documented detectable par- asitemia in infants younger than one month [7,13]. These studies were interpreted as showing either that transplacental transmis- sion of malaria occurs infrequently or that after transplacental transmission some ele- ments of immunity acquired from the mother protects infants [8]. It has been demonstrated that in hyperendemic areas, newborns more rarely become ill with malaria because of pas- sive maternal antibody and high levels of fetal hemoglobin [14,15]. Postulated mechanisms for congenital transmission include maternal transfusion into the fetal circulation either at the time of delivery or during pregnancy, direct penetra- tion through the chorionic villi, or penetration through premature separation of the placenta [16]. However, the effectiveness of the pla- centa to restrain malaria parasite passage to the fetus and the remarkable capacity of the fetus to resist infection has been demon- strated [17]. This resistance may reflect, among other things, the physical barrier of the placenta to infected red cells, the passive transfer of maternal antibodies, and the poor environment afforded by fetal erythrocytes for plasmodial replication due to their fetal hemoglobin composition and low free-oxy- gen tension [16-18]. It has been implied that transplacental transmission of malaria para- site and, consequently, congenital malaria seemed to occur rarely. However, increasing reports from many parts of sub-Saharan Africa consistently have indicated high prevalence of umbilical cord parasitemia ranging from 1.5 percent to 54.2 percent, and in some of these studies, there was a strong association between placental malaria and umbilical cord parasitemia [12]. Until recently, it was unclear whether the presence of P. falciparum malaria parasites in umbilical cord blood is an indication of ante- natally acquired infection or contamination with infected maternal blood at delivery. In a study in Kenya, it was unequivocally shown that malaria parasites identified in cord blood are acquired antenatally by transplacental transmission of infected erythrocytes and primigravid and secundigravid women with placental malaria are at increased risk for con- genital infection [19]. The high rate of transplacental transmission of malaria ap- pears to suggest the placental barrier is not very effective when infected with malaria parasites [8]. Perinatal mortality Placental malaria and its effects on peri- natal mortality (fetal or infant deaths from 28th week of pregnancy up to the seventh day after birth) have been investigated in various parts of sub-Saharan Africa. The im- pact of placental malaria on perinatal death (stillbirth and early neonatal death) is still under debate, and conflicting results have been obtained from various studies that in- vestigated the relationship between them. Newman et al. reported a seven-fold in- creased risk of stillbirth in association with placental parasitemia in areas with unstable malaria transmission in Ethiopia [20]. Mc- Gregor et al. [21] observed some seasonal differences in stillbirth rates, with the lowest rate occurring during the three months of the late dry season when placental malaria prevalence was low. Conversely, in a more recent study, Okoko et al. [22], in The Gam- bia, observed a two-fold increased risk of stillbirth among mothers with malaria-in- fected placenta and noted that placental malaria infection was independently associ- ated with a higher risk of delivering still- births in the population studied. The same conclusion was reached based on a meta-