Stress can lead to shorter pregnancies

Preparing for a baby can be stressful enough but now research among pregnant earthquake victims shows that undue stress during pregnancy can result in shorter pregnancies as well as a drop off in male babies.

The study looked at women in Chile during the 2005 Tarapaca earthquake to investigate just what the impact of such a stressful scenario was on the mothers-to-be.

Although previous studies have looked at stress on pregnant women, this is the first to look at the impact of the timing of that stress and its impact on the male-to-female birth rate.

It found that it is exposure to stress itself, rather than other factors than can often accompany or cause stress — such as poverty — that appears to impact on the pregnancy.

The researchers from New York University looked at the birth certificates of all babies born between 2004 and 2006 in Chile looking at information such as gestational age at delivery, sex, weight and height and whether medical intervention was required.

Factors such as mother’s age, marital status, if it was her first child and where within Chile she lived were also taken into account. This meant the researchers could look at differences among women living near the epicentre of the earthquake compared with those less affected.

"We were able to capture the developmental periods in which exposure to stress was most detrimental for either sex," said Professor Florencia Torche, associate professor of sociology at New York University and one of the authors.

The earthquake, which measured 7.9 on the moment-magnitude scale, was severe enough to be classified as ‘disastrous’.

Women who lived closest, and so experienced the worst of the earthquake during their second and third months of pregnancy, had a higher risk of delivering their babies pre-term (before 37 weeks of gestation).

Normally, about six in 100 women have a pre-term birth, but among women exposed to the earthquake in the third month of pregnancy, it rose by 3.4%, so that more than nine women in 100 delivered their babies early. It was most pronounced for female births; the chance of pre-term birth increased by 3.8% if the mothers were exposed to the quake in the third month, and 3.9% if it occurred in the second month. In contrast there was no statistically significant effect seen in male births.

Professor Karine Kleinhaus, said of the decrease in male births associated with this stress: "Generally, there are more male than female live births so out of every 100 births, 51 will be boys. Our findings show a 5.8% decline in this proportion, which would translate into a ratio of 45 male births per 100 births. This is a significant change for this type of measure."

Previous research, which has shown that women are more likely to miscarry male foetuses in stressful times, has suggested it is because male foetuses are larger and require more resources from the mother or that they are less robust.

This study’s authors suggest the placenta may be affected by the stress hormone cortisol which might impact on the placenta’s function.

Yahoo Lifestyle