Ultrasound scans have provided a conclusive evidence of malaria's effect on fetal growth. The study shows that malaria infection may lead to low birth weight.
The researchers studied almost 3,800 pregnancies for their study.
Low birth weight is the most important risk factor for neonatal mortality in developing countries. The research, carried out on the border of Thailand and Myanmar (Burma), highlights the importance of preventing malaria in pregnancy.
According to the World Malaria Report 2011, malaria killed an estimated 655,000 people in 2010. It is caused by parasites such as Plasmodium falciparum and Plasmodium vivax that are injected into the bloodstream by infected mosquitoes.
Malaria is one of the most common parasitic infections to affect pregnancy.
Researchers at the Shoklo Malaria Research Unit on the border of Thailand and Myanmar, part of the Wellcome Trust-Mahidol University-Oxford University Tropical Medicine Research Programme, have used ultrasound scans to provide the first direct evidence of the effect of malaria on fetal growth in pregnancies.
Antenatal ultrasound, which is essential for dating pregnancy accurately, is becoming more widely available in developing countries. The technology also allows doctors or locally trained workers to measure the diameter of the fetus's head.
For infections that occur in early pregnancy, the researchers believe that the size of the head may be the most appropriate indicator of growth restriction.
The ultrasound scans revealed that the diameter of the average fetus's head was significantly smaller when malaria infection occurred in the first half of pregnancy when compared to pregnancies unaffected by malaria.
On average, at the mid-pregnancy ultrasound scan the fetuses' heads were 2 percent smaller when affected by malaria. Even a single infection of treated P. falciparum or P. vivax malaria was associated with reduced fetal head diameter, irrespective of whether the woman had shown symptoms or not.
"By using antenatal ultrasound screening, we have provided clear evidence that malaria infection affects the growth of a child in the womb, even when the infection is caught early and treated. This can increase the risk of miscarriage and affect the child's health in later life," Dr Marcus Rijken, first author on the study said.
"Strategies to prevent malaria in pregnancy have focused on the second half of pregnancy, when most of the fetal weight gain takes place, but our works suggests that we need to broaden our efforts to focus on the first trimester, too.
"We need to make sure that pregnant woman are educated about the risks of malaria in pregnancy and where possible in areas of high risk, offer preventative medication from early pregnancy onwards," he said.
The study is published in the open access journal PLoS One.