Background. How anti-malarial antibodies are acquired and maintained during pregnancy and boosted upon reinfection with P. falciparum and P. vivax is unknown.Methods. A nested case-control study of 467 pregnant women (136 Plasmodium-infected cases and 331 uninfected controls) in northwestern Thailand was conducted. Antibody levels to P. falciparum and P. vivax merozoite antigens and the pregnancy-specific PfVAR2CSA antigen were determined at enrolment (median 10 weeks gestation) and throughout pregnancy until delivery.Results. Antibodies to P. falciparum and P. vivax were highly variable over time, and maintenance of high levels of anti-malarial antibodies involved highly dynamic responses resulting from intermittent exposure to infection. There was evidence of boosting with each successive infection for P. falciparum responses, suggesting the presence of immunological memory. However, the half-lives of Plasmodium antibody responses were relatively short compared to measles (457 years), and much shorter for merozoite responses (0.8 - 7.6 years) compared to PfVAR2CSA responses (36-157 years). The longer half-life of antibodies to PfVAR2CSA suggests that antibodies acquired in one pregnancy may be maintained to protect subsequent pregnancies.Conclusions. These findings may have important practical implications for predicting the duration of vaccine-induced responses by candidate antigens and supports the development of malaria vaccines to protect pregnant women.