The National Institutes of Health conducted a study that showed extreme temperatures as a factor in premature births. The correlation is valid for both hot and cold extremes occurring in the first seven weeks of pregnancy. The authors recommend pregnant women to avoid extreme temperatures.
Moreover, women that had been exposed to extreme temperatures during all the length of the pregnancy were also likely to deliver before the term.
The association was stronger when it came to extreme heat than it was the case with extreme cold. The authors think that during cold times, people can easily escape the cold by taking shelter.
The issues arise with high temperature when women are conditioned to use air conditioning, which is not compulsory, and some people might not afford its cost.
The Extreme Temperatures Study
A full-term pregnancy is considered to be between 39 and 40 weeks. On the other hand, a preterm birth happens before 37 weeks. Premature birth can lead to an increased risk of disability and infant death.
The authors cannot explain how extreme temperatures can influence the term of birth. One explanation may be that the development of the placenta may be affected. Another hypothesis is that the blood flow to the uterus might have been altered.
The study involved the medical records of 223,375 births in the US. The researchers correlated the data with hourly temperature information in the 12 regions where the births occurred.
The effect of temperature can vary from one person to another. Thus, the researchers decided to consider extreme heat to be above the 90th percentile of the area’s average, and extreme cold to be under the 10th percentile.
The Correlation
The results showed that women exposed to extreme cold in the first seven weeks of pregnancy were 20% at risk of delivering the baby before the 34th week of pregnancy. Moreover, 9% were more prone to give birth between the 34th and the 36th week, and 3% in the weeks 37 and 38.
When it comes to extreme heat, the risk was up to 11% for premature births that occurred before week 34, and 4% of births occurring in week 37 and 38.
The correlation was consistent with women being exposed to extreme temperatures later in their pregnancy.
The researchers say that an increase of hot days because of the climate change could raise the risk of premature births. The authors further recommend policy makers and health professionals to create interventions that will limit the exposure of pregnant women to extreme temperatures.
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