Abstract
BackgroundPlasmodium falciparum can be detected by microscopy, histidine-rich-protein-2 (HRP2) capture test or PCR but the respective clinical relevance of the thereby diagnosed infections in pregnant women is not well established.MethodsIn a cross-sectional, year-round study among 839 delivering women in Agogo, Ghana, P. falciparum was screened for in both, peripheral and placental blood samples, and associations with maternal anaemia, low birth weight (LBW) and preterm delivery (PD) were analysed.ResultsIn peripheral blood, P. falciparum was observed in 19%, 34%, and 53% by microscopy, HRP2 test, and PCR, respectively. For placental samples, these figures were 35%, 41%, and 59%. Irrespective of diagnostic tool, P. falciparum infection increased the risk of anaemia. Positive peripheral blood results of microscopy and PCR were not associated with LBW or PD. In contrast, the HRP2 test performed well in identifying women at increased risk of poor pregnancy outcome, particularly in case of a negative peripheral blood film. Adjusting for age, parity, and antenatal visits, placental HRP2 was the only marker of infection associated with LBW (adjusted odds ratio (aOR), 1.5 (95%CI, 1.0–2.2)) and, at borderline statistical significance, PD (aOR, 1.4 (1.0–2.1)) in addition to anaemia (aOR, 2.3 (1.7–3.2)). Likewise, HRP2 in peripheral blood of seemingly aparasitaemic women was associated with PD (aOR, 1.7 (1.0–2.7)) and anaemia (aOR, 2.1 (1.4–3.2)).ConclusionPeripheral blood film microscopy not only underestimates placental malaria. In this highly endemic setting, it also fails to identify malaria as a cause of foetal impairment. Sub-microscopic infections detected by a HRP2 test in seemingly aparasitaemic women increase the risks of anaemia and PD. These findings indicate that the burden of malaria in pregnancy may be even larger than thought and accentuate the need for effective anti-malarial interventions in pregnancy.
Highlights
Plasmodium falciparum can be detected by microscopy, histidine-rich-protein-2 (HRP2) capture test or PCR but the respective clinical relevance of the thereby diagnosed infections in pregnant women is not well established
Parity was strongly associated with low birth weight (LBW) and preterm delivery (PD), rates being more than double in primiparae than in multiparae (Table 1)
Placental malaria commonly is missed by standard microscopy of peripheral blood films
Summary
Plasmodium falciparum can be detected by microscopy, histidine-rich-protein-2 (HRP2) capture test or PCR but the respective clinical relevance of the thereby diagnosed infections in pregnant women is not well established. Pregnant women are a specific risk group for Plasmodium falciparum infection, malaria and related consequences [1]. This increased risk is partially due to physiological alterations of immunity. In pregnancy and by virtue of specific expression variants of the P. falciparum Erythrocyte Membrane Protein-1, parasite strains adhere to the syncytiotrophoblast, i.e. the surface lining the placental intervillous space. As immune recognition of and, response to these parasites are low in primigravidae susceptibility and clinical manifestation are increased. Protective immune mechanisms gradually develop and expand, and manifestation of infection declines [2,3,4]
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