Malaria infection during the earliest months of pregnancy stunts foetal growth even when the mothers do not have any malarial symptoms, according to a large-scale study conducted along the Thai-Burmese border.
"Malaria needs to be taken into account from the beginning of the pregnancy and not only in the last months before the birth," François Nosten, director of the Mae Sot-based Shoklo Malaria Research Unit (SMRU), which tracked 3,779 women's pregnancies from 2001-2010, told IRIN.
SMRU is attached to the Mahidol University-Oxford University Tropical Medicine Research Programme in Bangkok, which is supported by the UK-based health programmes donor, Wellcome Trust.
Pregnant women are among the most vulnerable to malaria infections as pregnancy reduces a woman's immunity, making her more susceptible to malaria infection and increasing the risk of illness, severe anaemia and death, according to the World Health Organization (WHO).
And while the impact of malaria on later stages of pregnancy and birth weight are well documented (increased risk of spontaneous abortion, stillbirth, premature delivery and low birth weight), the SMRU study is among the first to show a direct impact of malaria on early foetal growth, even in areas where malaria infections have plummeted.
Hidden parasite reservoir
People who have been repeatedly struck by malaria can develop partial immunity and may not have symptoms, despite harbouring the parasite.
And in communities where malaria infections have dropped (mainly due to prevention and treatment), the parasite level can also be so low as to not show up in tests, noted David Bell, head of malaria diagnostics at the Geneva-based research organization, Foundation for Innovative New Diagnostics (FIND).
Evidence that this hidden parasite reservoir can harm foetuses boosts the need for prevention even in areas that have already slashed infections, noted Andrea Bosman with the WHO Global Malaria Programme.
During pregnancy, the parasite hides in the placenta, rendering finger-prick blood tests inaccurate, Bell added. And while DNA analyses are more accurate, the technology is more expensive and less widely available.
Throughout most of sub-Saharan Africa, the WHO recommends giving anti-malarial drugs to pregnant women at intervals in case such a "hidden" malaria infection is present, but preventative treatment does not currently begin until after the first three months of pregnancy.
On average, at the mid-pregnancy ultrasound scan in the SMRU study, the diameter of the foetus's head - an indication of foetal growth - was 2 percent smaller when the woman was infected by malaria than if not.
The foetuses of close to 57 percent of the mothers infected with malaria had a smaller head than those who were not. Researchers said disrupted foetal growth can heighten the risk of pregnancy complications.
"The mother may not have any symptom of malaria and the reduction of the growth of the foetus is relative, not easily detected by ultrasound for individual cases [versus a large-scale study where the trend is more apparent]. The malaria infection nevertheless increases the risk of miscarriage, affects foetal growth and may hinder the child's development later in his life," said Nosten.
Detected early enough, it is possible to prevent the worst impacts of malaria, said Heidi Hopkins, a medical officer at FIND in Uganda.
"We can't necessarily 'reverse' the damage, but the earlier we diagnose and treat, the less time the foetus and mother are exposed to the infection, so the less impact it has."
With timely detection, "perhaps the growth of the foetus can catch up to compensate", added Nosten.
The challenge with early detection, noted Hopkins, is many women do not know they are pregnant until several weeks into the pregnancy.
FIND and the multi-agency Special Programme for Research and Training in Tropical Diseases (TDR) are testing new rapid diagnostic tests on pregnant women in Uganda and Burkina Faso, where malaria is more prevalent than in most parts of Southeast Asia, to learn whether earlier and affordable detection is possible during pregnancy.
"A preventive and safe medication to women from the beginning of their pregnancy should be evaluated where malaria is endemic," concluded Nosten.
Due to limited safety data, the WHO does not recommend the anti-malarial medication artemisinin during the first three months of pregnancy unless the "treatment is considered lifesaving for the mother and other treatments are considered unsuitable".
More than 50 million pregnancies occur in malaria-endemic areas annually, mostly in sub-Saharan Africa, according to the WHO.
An estimated 10,000 of these women and 200,000 of their infants die as a result of malaria infection during pregnancy, and severe malarial anaemia contributes to more than half of these deaths.