Toronto, April 1 (IANS): If you are pregnant and wish a full-term delivery, it is better to shift to a colder place before the mercury goes up as high temperature may reduce the length of your pregnancy, research indicates.

When temperatures reach 32 degrees celsius or higher over a period of four to seven days, the risk of early-term delivery is 27 percent higher than on typical summer days.

"Small-scale studies suggest that heat-induced stress increases uterine contractility, during a period of pregnancy when thermoregulation seems less effective," said Nathalie Auger from University of Montreal in Canada.

The human body maintains its core internal temperature through thermoregulation.

“We also suspect that dehydration resulting from high ambient temperature reduces the blood supply to the uterus, increasing the release of pituitary hormones that induce labour,” Auger explained.

The study involved data from 300,000 births that took place at Montreal in Canada between 1981 to 2010 with summer temperatures recorded by Environment Canada during this period.

They found that extreme heat did not seem to increase the number of pre-term births, but in women who reached 37 or 38 weeks of pregnancy, the risk of early-term delivery increased by 17 percent following a three-day episode of 32 degrees celsius or more, compared to days without a heat wave.

When the extreme heat episode lasted from four to seven days, the risk reached 27 percent, found the researchers.

"Early-term newborns are also at greater risk of death," Auger said.