Academic journal article Environmental Health Perspectives

Pregnancy Pause: Extreme Heat Linked to Shortened Gestation

Academic journal article Environmental Health Perspectives

Pregnancy Pause: Extreme Heat Linked to Shortened Gestation

Article excerpt

Pregnancy tends to make women more vulnerable to heat stress. Added fat deposits and the attendant decrease in the ratio of body surface area to body mass mean a woman's body is less able to cool off by losing heat to the environment. Heat stress has been linked in earlier studies to induction of uterine contractions, increased secretion of the childbirth-related hormones oxytocin and prostaglandin F (2[alpha]), and increased levels of heat-shock protein 70 (which has been linked to preterm delivery). A new study now suggests maternal exposure to extreme heat may have an immediate effect on pregnancy duration [EHP 119(10):l449-l453; Dadvand et al.].

The Spanish-based research team analyzed birth data for 7,585 women who delivered at the Hospital Clinic of Barcelona between January 2001 and June 2005. They used national data on daily heat and temperature to calculate which days during that period exceeded the 90th ([HI.sub.90]), 95th ([HI.sub.95]), and 99th ([HI.sub.99]) percentiles for % heat index for the longer period of 1983-2006.

Pregnancies ranged from 22.2 to 43.5 weeks, with an average of 40 weeks. The results showed that all three HI percentiles were associated with a reduction in pregnancy duration. An [HI.sub.90] episode on the day before delivery (lag 1) was associated with a 1-day reduction in average pregnancy duration, a lag 1 [HI. …

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