Saw Oo Tan, Rose McGready, Julien Zwang, Mupawjay Pimanpanarak, Kanlaya Sriprawat, Kyaw Lai Thwai, Yoe Moo, Elizabeth Ashley, Bridget Edwards, Pratap Singhasivanon, Nicholas White, Francois Nosten

Abstract

Haematological changes associated with malaria in pregnancy are not well documented, and have focused predominantly on anaemia. Examined here is thrombocytopaenia in pregnant women infected with Plasmodium falciparum or Plasmodium vivax in a low transmission area on the north-western border of Thailand.
METHODS: In this observational study, the platelet counts was reviewed from routine complete blood counts (CBC) in a cohort of healthy and malaria infected pregnant women attending weekly antenatal clinics. In a previously published cohort study of Karen pregnant women (n=723), every woman had a CBC on admission. A platelet count of 75,000 /muL was the value at two standard deviations below the mean and this value was used to indicate thrombocytopaenia for this study. Differences in platelet count in non-pregnant and pregnant women were compared after matching for age, symptoms, malaria species and parasitaemia.
RESULTS: In total 974 pregnant women had 1,558 CBC measurements between February 2004 and September 2006. The median platelet counts (/muL) were significantly lower in patients with an episode of falciparum 134,000 [11,000-690,000](N=694) or vivax malaria 184,000 [23,000-891,000](N=523) compared to healthy pregnant women 256,000 [64,000-781,000](N=255), P< .05 for both comparisons. Plasmodium falciparum and P. vivax caused a 34%(95% CI 24-47) and 22%(95% CI 8-36) reduction in platelet count, respectively. Pregnant compared to non pregnant women were at higher risk (OR=2.27, 95%CI 1.16-4.4, P= .017) for thrombocytopaenia. Platelets counts were higher in first compared with subsequent malaria infections within the same pregnancy. Malaria associated thrombocytopaenia had a median [range] time for recovery of 7 [2-14] days which did not differ by antimalarial treatment (P= .858), or species (P= .632) and was not associated with active bleeding.
CONCLUSION: The thrombocytopaenic effects of acute uncomplicated falciparum and vivax malaria are significant. Pregnant women are more susceptible to thrombocytopaenia than non-pregnant women. Uncomplicated malaria associated thrombocytopaenia was never severe in this series and prompt treatment resulted in normalization of platelet counts within a week.