A new study has discovered that pregnant women who are constantly exposed to unusually cold or hot weather stand at risks of having babies with low birth weight, even when the baby was not born prematurely.
With the increasing threat of global warming and the occasional significant changes in weather events and conditions, the outcome of this research underscores the need to carry out further studies as well as public health campaigns of the potential negative effects of extreme local weather conditions during pregnancy, the study group warned.
To carry out the study, the group of researchers analysed data from more than 220,000 babies delivered at 19 US hospitals, from 2002 to 2008. Using weather statistics, the scientists tried to determine the daily weather conditions in the regions round about each hospital, then they estimated the average temperatures throughout the full pregnancy period, as well as for each trimester.
The research scientists wanted to know if ambient weather conditions could impact the risk that a pregnant woman could have a child with ‘term low birth weight’ — often referred to babies who arrive at 37 weeks of pregnancy or later, but with less than 5.5 lbs weight.
For a more accurate result analysis and application, the researchers defined ‘unusually cold weather’ as temperatures under 5th percentile of average temperatures of the study region; while ‘unusually hot weather’ was classified as temperature above 95th percentile of normal weather condition of the study region.
It implied that the study team considered what is unusually cold or unusually hot on the basis of where the women lived during their pregnancy.
The outcome of the study showed that women who were exposed to extreme cold temperatures during the second and third trimesters, or extreme hot weathers during the third trimester of their pregnancy, were 18 to 31 percent more likely to have term low-birth-weight babies. This results contrasts with women who were exposed to warmer temperature during the second and third trimesters of their pregnancy.
Also, women who were exposed to extreme hot or cold temperatures throughout the period of their pregnancy were 2.5 times more likely to have term low-birth-weight babies, in contrast with those exposed to warmer weather conditions throughout their pregnancy period.
Study senior author, Pauline Mendola advised that pending the result of further studies, pregnant women should reduce the amount of time they are exposed to harsh weather conditions.
Mendola, an epidemiologist at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) recommended that expectant women should, for example, as much as possible avoid staying outdoors for prolonged periods when there is extreme heat or cold weather conditions.
According to the researchers, low-birth-weight babies are born that way typically because of their genetic predisposition to small size, or because they experienced illness, infection or a failure to develop in the womb.
However, the scientists couldn’t figure why exposure to extreme hot or cold temperature during pregnancy could shrink the size of a new born baby. However, they stated that one possibility is that unusually cold or hot weather conditions could limit blood flow to the uterus, which could stunt fetal growth.
The study took into account factors that could affect a baby’s weight at birth, such as the sex of the child and the mother’s body mass index. But the result of the new scientific discovery remained consistent, regardless.