Low-level Plasmodium falciparum infections may not cause full-blown malaria symptoms, but they could still affect pregnant women. Researchers at the Institut de recherche pour le développement (IRD; Institute for Development Research) and the Centre d’Étude et de Recherche sur le Paludisme Associé à la Grossesse et l’Enfance (CERPAGE; Centre for Study and Research on Pregnancy-Associated Malaria and Infancy) have used polymerase chain reaction (PCR) to help them understand more about the impact. The research, which is the first study to assess the impact of submicroscopic malarial infections in pregnant women, was published in Clinical Infectious Diseases.


Low-level, known as occult, infections with P falciparum are common in pregnant women in Benin. These diagnosed using molecular (rather than microscopic) techniques. The study looked at 1037 pregnant women in south-west Benin between May 2008 and May 2011, and measured the baby’s gestational age using ultrasound, and the mother’s infection with P falciparum, using microscopy and PCR. The researchers (IPTp), maternal anaemia, and the rates of premature birth and low birth weight.

While microscopy found that 16% of women were infected, this increased to 40% using PCR. The submicroscopic infections found using PCR were linked with significantly increased risks of anaemia and low birth weight in women pregnant for the first time, and around a doubling of the risk of premature births in women with more than one child.

These results show that sensitive diagnostic techniques such as PCR can improve the rate of diagnosis, but that advances still need to be made to improve the rate They also show that preventing malaria infections could improve the health of women and their babies, particularly in women in their first pregnancy, and support the WHO recommendations to scale-up the number of intermittent preventive treatment doses received by women during pregnancy.