Malaria is endemic in more than 100 countries. Over two billion people living in these endemic countries are exposed to P. falciparum infection. Children less than 6 years old and pregnant women are at increased risk of P. falciparum malaria and its associated complications. Approximately 50 million women become pregnant every year in malaria endemic regions.64 Pregnancy-associated malaria is estimated to be responsible for a third of preventable low birth weight babies in sub-Saharan Africa and to cost the lives of approximately 200,000 infants annually.65 Women are more susceptible to infection when pregnant, and both the frequency and the severity of the disease are higher in pregnant than non-pregnant women.1 In areas where malaria is highly endemic, a protective semi-immunity against P. falciparum is acquired during the first 10–15 years of life with the majority of malaria-related morbidity and mortality happening in young children.66 However, in contrast with low malaria prevalence in adults, pregnant women in endemic areas are highly susceptible to malaria.1
In pregnancy, there is a transient depression of cell-mediated immunity that allows fetal allograft retention but also interferes with resistance to various infectious diseases.67 Cellular immune responses to P. falciparum antigens are depressed in pregnant women in comparison with non-pregnant control women.65,68
Anti-adhesion antibodies against chondroitin sulfate A-binding parasite are associated with protection from maternal malaria, but these antibodies develop only over successive pregnancies, accounting for the susceptibility of primigravidae to infection.69 Indeed, women in first and second pregnancies are the most affected, with both gravidity and premunition influencing susceptibility to malarial infection.70
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