Being too hot or cold during pregnancy 'may increase the risk of premature birth' [MUST READ]

 Being too hot or cold during pregnancy could increase the chance of the baby being born prematurely, a study suggests.

Living an in extremely hot or cold area during the first seven weeks of pregnancy was linked with an early delivery, researchers found.

Women exposed to extreme heat for most of the time they were expecting were also more likely to give birth before their due date. 

The researchers said it is not known exactly why drastic temperatures leads to a baby being delivered early.

They believe the stress of being too too hot or cold may hinder the development of the placenta or alter blood flow to the uterus, both of which may lead to an early labour.

Being too hot or cold during pregnancy could increase the chance of the baby being born prematurely, a study suggests (file photo)

'Our findings indicate that it may well be prudent to minimize the exposure of pregnant women to extremes in temperature,' said the study's senior author, Dr Pauline Mendola, of the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD).

A pregnancy is considered full term at between 39 and 40 weeks.

Preterm birth occurs before 37 weeks of pregnancy and increases the risk of risk of infant death, asthma, lung problems and long-term disability.

To come to their conclusions, the researchers linked electronic medical records from 223,375 births at 12 clinics throughout the US to hourly temperature records for the region surrounding each one.

THE CURSE OF BEING A PREMATURE BABY: THOSE BORN EARLY 'EARN LESS AND HAVE WORSE HEALTH LATER IN LIFE' 

People-born prematurely are more likely to grow up to be poor - in terms of both wealth and well-being, a study has claimed.

Fewer adults who were 'sugar-bag babies' - born prematurely at low-birth weights - were employed or had children, researchers found. 

And they were also more likely to have lower incomes, be single and report more chronic health conditions than their normal-birth-weight-term counterparts.

The researchers said the first generation of extremely low-birth-weight (ELBW) premature babies - weighing less than 1,000 grams (2.2 lbs) - who were born after the introduction of neonatal intensive care has now survived into their fourth decade.

Dr Saroj Saigal, of McMaster University in Canada, compared the functioning of adults aged 29 to 36 who were ELBW with adults who are born at normal weight at term.

The team noted that what constitutes a hot or cold temperature varies from person to person and place to place.

Therefore, they calculated the average temperatures of all the areas, and then defined extreme cold temperatures as below the 10th percentile of the average.

Extreme heat was defined as above the 90th percentile.

The researchers found women who experienced extreme cold for the first seven weeks of their pregnancies had a 20 per cent higher risk for delivering before 34 weeks of pregnancy.

They also had a nine per cent increased risk for delivering from 34-36 weeks, and a three per cent increased risk for delivering in weeks 37 and 38.

Women whose first seven weeks of pregnancy coincided with extreme heatwaves had an 11 per cent increase in risk before 34 weeks, and a four per cent increased risk at 37 to 38 weeks.

Living in an extremely hot place for the duration of pregnancy was linked with a raised risk of the baby being delivered at 34 weeks and 36-38 weeks by 6 to 21 per cent respectively.

They found no link with being exposed to cold throughout a time a woman was expecting.

Researchers believe this could be because during cold weather, people are more likely to seek shelter and so can escape the cold's effects more easily.

During heatwaves, people are more likely to endure the temperature, particularly if they cannot afford air conditioning.

The researchers theorize the stress of being too too hot or cold could hinder the development of the placenta or alter blood flow to the uterus, both of which may lead to an early labour

The team said climate change could lead to a spike in the rate of babies being born preterm due to an increase in the number of extremely hot days.

The findings should spur doctors to devise interventions to minimise pregnant women's exposure to extreme temperatures.

They also called for more research to understand how temperature extremes might increase preterm birth risk.

The study was published in the journal Environmental Health Perspectives.