Malaria is an important cause of maternal and perinatal morbidity and mortality [
1]. Pregnancy-associated malaria (PAM) is characterized by the accumulation of
Plasmodium falciparum-infected erythrocytes (PfIE) in placental intervillous spaces [
2]. The occurrence of low birth weight (LBW) is one of the main consequences of PAM and this is associated with a high risk of neonatal mortality. Approximately 100,000 children die annually in sub-Saharan Africa due to malaria-related LBW [
3].
In Benin, anti-malarial treatment policy has long been based on the use of chloroquine (CQ) as first-line and SP as second-line. CQ was also used in prophylaxis of malaria during pregnancy. However, decreased therapeutic efficacies of both CQ and SP prompted the change of the national anti-malarial drug policy in 2004 by the official withdrawal of CQ and SP in the treatment of uncomplicated malaria. As reported in many parts of the world sulphadoxine-pyrimethamine (SP) has been used extensively in the past for treatment and prophylaxis of falciparum malaria [
4]. One of the consequences is that the utility of SP in the treatment of malaria in sub-Saharan Africa has declined drastically in the last decade because of the emergence and spread of drug resistance of
P. falciparum. However, SP is still used for malaria prevention during pregnancy as intermittent preventive treatment in pregnancy (IPTp). The SP-IPTp regimen has been recommended by the World Health Organization (WHO) [
5] since 2004, and was adopted by Benin the same year. SP-IPTp regimen comprises the administration of at least two curative doses of SP starting in the second trimester of pregnancy (16 weeks of gestation) and ensuring a dose spacing interval of at least one month. SP continues to be the drug of choice for IPTp both because it is safe, easy to administer, and because a single treatment dose has long-lasting prophylactic effect (up to 60 days) [
6,
7]. SP efficacy is dependent on the number of mutations accumulated in the genes encoding the
P. falciparum enzymes dihydrofolate reductase (DHFR) and dihydropteroate synthase (DHPS) [
8,
9]. Single nucleotide polymorphisms (SNPs) in the
pfdhfr gene, at codons 51, 59, 108, and 164, and in the
pfdhps gene, at codons 436, 437, 540, 581, and 613 are associated with
in vitro resistance to pyrimethamine and sulphadoxine, respectively [
10‐
12]. Parasite resistance to SP
in vivo is largely associated with a triple mutation in
pfdhfr (resulting in amino acid changes; N51I, C59R and S108N) coupled with a double mutation in
pfdhps (A437G, K540E) [
13‐
15]. Such
P. falciparum parasites carrying quintuple mutations (triple
pfdhfr with double
pfdhps mutations) are highly prevalent in East Africa [
16,
17], but rare in West Africa [
18], including Benin where a study from 2003 to 2005 showed that the most prevalent haplotype (85%) was the quadruple (triple
pfdhfr, single
pfdhps) mutant [
19]. Although SP shows poor efficacy in children infected with quintuple mutant parasites, IPTp with SP seems to remain effective in preventing the adverse consequences of malaria on maternal and foetal outcomes in areas where a high proportion of
P. falciparum parasites carry these quintuple mutations [
20,
21].
From 2005 to 2007, a study in southern Benin [
22] showed that the proportion of parasites carrying quadruple
pfdhfr/
pfdhps mutations during pregnancy was constantly above 80% whilst no quintuple mutants were detected. Recently, a prospective cohort study (STOPPAM) on ~1,000 pregnant women in south-western Benin, four years after the change of malaria treatment policy in Benin was conducted. A subset of samples collected during the follow up were used to assess the prevalence and possible selection of molecular markers of SP resistance in the
pfdhfr and
pfdhps genes present at different gestational ages, and to characterize recurrent infections in the context of SP-IPTp.