A new condition has been added to the growing list of the impacts of climate change on humans. A new study shows that pregnant women exposed to low number of rains and more hot days are more likely to deliver newborns with lower birth weight and more vulnerable to health risks.

The researchers examined 19 African countries within two years and found that in the early stage of pregnancy, climate change could potentially affect birth outcomes. The severity of the impact depends on the current location of the pregnant woman, but the effect has been found to appear in all developing countries.

The new study is the first of its kind to analyse the effect of rain and temperature on birth weight. The researchers looked into the climate data and extensive health data from African countries to analyse climate change and its effects on birth weight.

According to the World Health Organisation, infants are considered of low birth weight if born under 2,500 grammes, and those diagnosed with low birth weight are at higher risk of mortality due to being more prone to illness and disabilities. Those infants are also at risk of being less likely to attain the education and income of an infant born within a healthy weight range.

The health risks of low birth weight infants also cause financial burden. In developing countries where medical support services are mostly uncommon, the total cost of hospitalisation, returning for medical services, and long-term morbidity caused by low birth weight are all impactful, adding the social stigma of having physical disability.

Almost 70,000 births in 19 African countries between 1986 and 2010 were examined for the study. The researchers took into account seasonal rainfall and air temperatures in each areas, as well as the mother’s status, like education level and if electricity is available on the household.

The United States Agency for International Development funded the study, and in 2013, the researchers combined health data from the Demographic and Health Surveys and the increasing and livelihood zone information from the agency’s Famine Early Warning System programme. The precipitation data from the Climate Hazards Group InfraRed Precipitation was also included.

It has been found that an increase of above 100°F on hot days during any trimester caused the decrease in birth weight, and even a single extra day of above 100°F in the second trimester causes a 0.9g weight reduction. The impact of the temperature turns greater when it increased to 105°F.

Aside from high temperature, higher amounts of precipitation during any trimester were also proven to influence birth weight. Higher number of rains helped women to deliver babies with higher birth weight, and the average of 10mm increase in rains also increases birth weight by around 0.3-0.5g.

"While the results are dependent on trimester and location, the data shows that climate change--a combination of increased hot days and decreased precipitation--correlate to lower birth weights," said Kathryn Grace, a geography professor at the University of Utah, in a statement. Grace suggests that immediate efforts to combat the “evident stresses caused by climate change” are needed, as "services such as education, clean water efforts and nutrition support won't be as effective.”

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