"Malaria in pregnancy has been recently prioritised by the EC 7th Framework Program. In response, we propose to carry out a cohort observational study in pregnant women in 5 P. vivax endemic countries, broadly representing most of the world's infections. The Indian and Papua New Guinean endemic sites are included because of their important contribution to the global burden of vivax malaria; PNG has a high prevalence of asymptomatic P. vivax infections resembling P. falciparum infection in sub-Saharan Africa, and India contributes to nearly 80% of malaria cases in Southeast Asia. In Latin America, 3 countries are selected, Guatemala, Colombia and Brazil. In Guatemala P vivax is responsible for almost all malaria cases, in Colombia and Brazil it co-exists in different proportions with falciparum. Pregnant women will be enrolled at each site during routine antenatal care visits (ANC) and followed-up at the health facility until delivery or end of pregnancy. P. vivax malaria parasitaemia will be assessed at enrolment, at every contact with the health facility and at delivery. In a sub-sample of women, peripheral blood will be taken for immunological/molecular studies, and placental samples will be collected. To assess with precision the prevalence of infection (estimated to be around 4% on average) and to obtain sufficient number of pregnant women with P vivax infection to determine the impact on birthweight, 2000 pregnant women per site will be enrolled. Due to the likely low prevalence of infection in pregnancy, the number of pregnant women with P. vivax per site will probably not be enough to assess specific impact for each site, thus a multicentric study design will be used. Immunological analysis will be performed to unveil whether there are pregnancy-specific immune responses. Phenotypic and genotypic analyses of parasites from the placenta should reveal their adhesive properties and whether the accumulation of infected erythrocytes unique parasite population."