New research reveals how important it is for pregnant women to avoid stressful life situations due to its potential adverse effects on their male offspring.

Specifically, researchers found that stressful life events during the first 18 weeks of pregnancy are associated with reduced sperm quality and lower testosterone count in male offsprings when they hit adulthood.

A 20-Year Study

In a study published in the journal Human Reproduction, a team of international researchers observed 643 men who are aged 20.

Data were also used from Western Australia's Raine Study, a multi-generational study in which nearly 3,000 women in their 18th week of pregnancy from May 1989 to November 1991 reported stressful life events during the first four months of pregnancy.

Stressful life events include, but are not limited to, the death of a close relative or friend, separation, divorce, or marital problems, problems with children, involuntary job loss of mother's or partner's involuntary job loss, money problems, pregnancy concerns, and moving home problems.

Out of the 1,454 boys born to the mothers who were part of the study, 643 underwent a testicular ultrasound examination and provided semen and blood samples when they reached 20 years old.

The Results

Findings show that 63 percent of the men were exposed to at least one stressful life event during early gestation, which is at zero to 18 months into the pregnancy. Compared to those who were not exposed to events, these men were found to have lower total sperm counts, fewer sperm that could swim well, and lower concentrations of testosterone.

Additionally, men exposed to three or more of these stressful life events during early gestation were found with an average of 36 percent lower sperm count than those who weren't exposed. There was also a 12 percent decrease in sperm motility as well as an 11 percent decrease in testosterone levels, according to study senior author Professor Roger Hart of the University of Western Australia.

"This suggests that maternal exposure to stressful life events during early pregnancy, a vulnerable period for the development of male reproductive organs, may have important life-long adverse effects on men's fertility," Hart added. "This contrasts with the absence of any significant effect of exposure to maternal stressful life events in late gestation."

However, Hart stressed that while their team found a link between stressful life events in early pregnancy and reduced sperm quality and testosterone concentrations in offspring, it doesn't mean that one definitely causes the other. It's unlikely to be the only cause of male infertility, but combined with other factors, it could increase the risks for adverse effects.