| Health / Health News |
Extreme temperatures could increase preterm birth risk
NIH | SEPTEMBER 16, 2016
Extreme hot or cold temperatures during pregnancy may increase the risk of preterm birth, according to study by researchers at the National Institutes of Health.
Extreme temperatures could increase preterm birth risk. 
The researchers found more consistent associations with early delivery after exposure to extreme heat than to extreme cold weather. They theorized that, during cold spells, people are more likely to seek shelter and so could more easily escape the cold’s effects. But during extreme heatwaves, people are more likely to endure the temperature, particularly when the cost of or access to air conditioning is an impediment.
A pregnancy is considered full term at between 39 and 40 weeks. Preterm birth occurs before 37 weeks of pregnancy and increases the risk for infant death and long term disability.
It is unknown why extremes of hot or cold might influence preterm birth risk. However, the researchers theorize that the stress of temperature extremes could hinder the development of the placenta or alter blood flow to the uterus, both of which could potentially lead to early labor.
The researchers found that women who experienced extreme cold for the first seven weeks of their pregnancies had a 20 percent higher risk for delivering before 34 weeks of pregnancy, a nine percent increased risk for delivering from 34-36 weeks, and a three percent increased risk for delivering in weeks 37 and 38.
Women whose first seven weeks of pregnancy coincided with extreme heatwaves had an 11 percent increase in risk before 34 weeks, and a four percent increased risk at 37 to 38 weeks.
Exposure to extreme heat during weeks 15-21 increased the risk for delivery at 34 weeks and at 34-36 weeks by 18 percent and for delivery from 37 to 39 weeks by four percent. Hot exposures during weeks 8-14 increased the risk for birth at 37 to 38 weeks by 4 percent.
Overall, exposure to extreme heat for the duration of pregnancy was associated with increases in risk for delivery at 34 weeks and 36-38 weeks by 6 to 21 percent.
An increase in the number of extreme hot days due to climate change could lead to increases in the preterm birth rate.
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