Researchers evaluated the medical data of 643 20-year-old men whose mothers had previously self-reported information on stress during pregnancy. They discovered that 63 percent of the men had been exposed to a stressful event during early gestation, and these same men had symptoms of diminished fertility.
Lower sperm counts, fewer sperm that could swim well, and lower testosterone concentrations were reported in men exposed to stressors in the womb at 0 to 18 weeks compared to men who were not exposed or were only exposed to stress between 18 and 34 weeks of gestation. Overall, fewer stressful events occurred during later gestation.
The findings, published in Human Reproduction correlate with what we know about fetal growth: During the first few months of pregnancy is when male reproductive organs are at a crucial stage of development.
"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. This contrasts with the absence of any significant effect of exposure to maternal stressful life events in late gestation," Roger Hart, a professor at the University of Western Australia and medical director of the Fertility Specialists of Western Australia IVF, said in a statement.
The study included multigenerational figures on about 3,000 women recruited between 1989 and 1991. Women in the study completed questionnaires at 18 and 34 weeks' gestation.
The researchers adjusted their analyses to take into account significant factors, such as the mothers' body mass index and socioeconomic status, and whether the mothers had previously given birth.
Stressful events included death of a family member or friend; separation, divorce, or marital problems; challenges with children; involuntary loss of employment; money problems; pregnancy concerns; and relocating, among others.
The inability to measure resilience – individual reactions to stress – along with the information being self-reported, could have limited the accuracy of the results.
The impact of stress on sperm and testosterone
The link between high-stress events while in the womb and diminished reproductive function could shed more light on sperm count declines in men. However, apart from genetic and physical damage, the sperm count decreases have been mostly unexplained, the researchers say.
The link between stressful life events in early pregnancy and reduced sperm quality and testosterone are just that – a link, they claim. The researchers have not found that stress causes infertility.
While a male baby's exposure to stress during early gestation is probably unlikely to cause infertility, it could contribute to an increased risk when there are other factors at play, such as smoking, obesity, or blood fat levels. There has been previous research that links extreme stress during early pregnancy to fertility impairments in men.
"Our findings suggest that improved support for women, both before and during pregnancy, but particularly during the first trimester, may improve the reproductive health of their male offspring," professor Hart added.
Thankfully, you can find plenty of good resources on how to manage stress and anxiety during pregnancy.