Umbilical cord-blood infections with Plasmodium falciparum malaria are acquired antenatally in Kenya.

BACKGROUND It is unknown whether the presence of Plasmodium falciparum malaria parasites in umbilical cord blood denotes infection acquired antenatally or contamination with infected maternal blood at delivery. METHODS Parasites were quantified by real-time quantitative polymerase chain reaction (RTQ-PCR) and were genotyped in paired maternal- and cord-blood samples obtained from 632 pregnant Kenyan women and their newborns. Placental alkaline phosphatase (PLAP) and polyclonal immunoglobulin E levels were also quantified in paired maternal- and cord-blood samples, as markers of admixture of maternal blood with cord blood. RESULTS Sixty-six cord-blood samples (10.4%) contained falciparum malaria, as detected by RTQ-PCR. For 25 of the infected cord-blood samples, either absence of infection was noted in paired maternal-blood samples at delivery (n=16) or amplicon levels in cord-blood samples were 10-fold higher than those in maternal-blood samples (n=9). Of the paired maternal- and cord-blood samples that were both infected, 57% showed discordant malaria parasite strains. There was no correlation between maternal parasitemia and levels of PLAP and immunoglobulin E in cord blood. PLAP levels, however, were significantly higher in cord-blood samples obtained from newborns of primigravid or secundigravid women with placental malaria, compared with cord-blood samples obtained from newborns of women without placental malaria or multigravid women. These findings indicate that parity and placental malaria are risk factors for maternofetal transfusion. CONCLUSIONS Malaria parasites identified in cord blood are acquired antenatally by transplacental transmission of infected erythrocytes. Primigravid and secundigravid women with placental malaria are at increased risk for congenital infection.