Washington:
A pregnant woman's exposure to reduced precipitation and an increased number of very hot days may result in lower birth weight of the child, according to researchers, including one of Indian-origin.
In a first-of-its-kind study, the researchers examined the relationship among precipitation, temperature and birth weight in 19 African countries.
"Our findings demonstrate that in the very early stages of intra-uterine development, climate change has the potential to significantly impact birth outcomes," said Kathryn Grace, professor at University of Utah.
"While the severity of that impact depends on where the pregnant woman lives, in this case the developing world, we can see the potential for similar outcomes everywhere," said Grace.
Other authors of the study include Frank Davenport, Christopher Funk and Shraddhanand Shukla from University of California.
With the inaccuracy of determining exactly when a pregnancy began in rural countries which lack pregnancy tests and the inability to measure characteristics like a newborn's cognitive development, low birth weight is the most reliable measure of whether a pregnancy has been negatively affected by an external factor.
Low birth weight is defined by the World Health Organisation as any baby born under 2,500 grammes.
Low birth weight infants are more susceptible to illness, face a higher risk of mortality, are more likely to develop disabilities and are less likely to attain the same level of education and income as an infant born within a healthy weight range.
In total, the team examined nearly 70,000 births in 19 African countries between 1986 and 2010 and matched these births with seasonal rainfall and air temperatures, as well as variables describing the mother and mother's household, such as education level and whether the household had access to electricity.
This is the first time researchers utilised fine-resolution precipitation and temperature data alongside birth data to analyse how weather impacts birth weight.
Researchers found that an increase of hot days above 37.7 degree Celsius during any trimester corresponds to a decrease in birth weight.
Just one extra day with a temperature above 37.7 degree Celsius in the second trimester corresponded to a 0.9 g weight decrease. This result held with a larger effect when the temperature threshold was increased to 40.5 degree Celsius.
Conversely, higher amounts of precipitation during any trimester resulted in larger birth weights.
On average, a 10 mm increase in precipitation during a particular trimester corresponds to an approximate increase in birth weight of around 0.3-0.5 grammes.
The study was published in the journal Global Environmental Change.