Earthquakes 'trigger early births'

Earthquakes, like this one in Turkey, linked to early births

Stress caused by being in an earthquake could cause mothers to give birth early, researchers claim.

They suggest that if the earthquake strikes early in pregnancy, the trauma caused may "activate a clock" in the placenta.

Stress may activate a clock in the placenta which determines the time of gestation

Laura Glynn, University of California

A team at the University of California at Irvine looked at the 1994 Los Angeles earthquake which measured 6.7 on the Richter scale. It killed 50 people and caused an estimated $40bn in property damage.

Of 40 women studied, five who had been in their first trimester at the time of the disaster delivered their babies on average at 38.05 weeks, compared with the 38.99 week average for eight women who were in their third trimester.

The study also looked at 11 women who had already delivered their children when the earthquake hit. They delivered their babies on average at 39.49 weeks.

The normal gestation period is 40 weeks.

Laura Glynn, one of the researchers, said: "We have a theory that stress may activate a clock in the placenta which determines the time of gestation."

She said the placenta was not just a passive filter between mother and foetus as had previously been believed.

It was an endocrine organ that responded to stimuli and produced hormones and peptides during pregnancy which circulated in both the maternal and foetal bloodstreams, she said.

Gestation

This helped influence the physiological mechanism that times the length of gestation.

Stress - not only the environmental type associated with earthquakes, but also marital or job stress - was likely to affect the placental clock and shorten gestation, she said.

Glynn said the study also showed that emotional responses to stress are greater earlier in pregnancy.

Women in their first trimester during the earthquake rated it as "extremely upsetting" whereas those who experienced it during the third trimester found it only "moderately" upsetting, she said.

Stress has also been linked in previous research with premature births and birth defects including visual, hearing and intellectual impairments, as well as complications in the respiratory, gastrointestinal and renal systems.

There are also some findings showing that stress can increase the likelihood of miscarriage but because so many early miscarriages go undetected, they are more difficult to study and data is not easily available.

The evidence was presented at a meeting of the American Psychological Society in Miami.

The National Childbirth Trust in the UK was not surprised at the finding that stress affected pregnancy.

But a spokeswoman added: "We welcome any research which allows us to address the physiological process of pregnancy and childbirth so we can have more information to help us to give women the support they need."