Washington: Stress during early pregnancy is linked to reduced reproductive function in male offspring, a recent study suggests. The findings suggest that men, whose mothers were exposed to stressful life during the first 18 weeks of pregnancy, may have reduced sperm counts when they become adults.
The research suggested that the initial months of pregnancy is when male reproductive organs are at their most vulnerable stage of development. As part of the study, the researchers studied 643 young men aged 20 and found that those who were exposed to at least one stressful life event inside their mother's womb during early gestation (0-18 weeks) had worse sperm quality and lower testosterone concentrations than those who were not exposed, or who were exposed during later gestation, between 18-34 weeks.
The findings come from Western Australia's Raine Study, a multi-generational study that recruited nearly 3000 women in their 18th week of pregnancy in the period between May 1989 and November 1991. The mothers completed questionnaires at 18 and 34 weeks' gestation, and each survey included questions about stressful life events during the preceding four months of pregnancy. These events included the death of a close relative or friend, separation or divorce or marital problems, problems with children, mother's or partner's involuntary job loss, money problems, pregnancy concerns, moving home or other problems.
A total of 2868 children (1454 boys) were born to 2804 mothers and were followed by the researchers, making this the first study to investigate prospectively the links between exposure to stressful life events in early and late gestation and male reproductive function in young adult men. When they reached 20, up to 643 young men underwent a testicular ultrasound examination and provided semen and blood samples for analysis.
The researchers found that 63 per cent of the men had been exposed to at least one stressful life event in early gestation, while fewer stressful life events occurred in late gestation. Those who were exposed to stressful life events in early gestation had lower total sperm counts, fewer sperms that could swim well and lower concentrations of testosterone than those exposed to no events.
The researchers adjusted their analyses to take into account factors that could affect their calculations, such as the mothers' body mass index, socioeconomic status and whether or not the mothers had given birth previously.
The team of researchers found that men who had been exposed to three or more stressful life events during early gestation had an average of 36 per cent reduction in the number of sperm in their ejaculate, a 12 per cent reduction in sperm motility and a 11 per cent reduction in testosterone levels compared to those men who were not exposed to any stressful life event during that period.
According to the researchers, 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.
"These potential associations could provide important insight into the decline of total sperm count in Western men, which has been, apart from genetic and direct spermatogenic damage, largely unexplained," said authors of the study published in the Journal of Human Reproduction.