Runners of the world take note: A recent study published June 5, 2019 in Science Advances suggests that a woman who carries a baby to term expends an amount of energy that’s roughly equivalent to someone running a 40-week marathon.
To arrive at that conclusion, researchers gathered measurements of total energy expenditure (TEE) and basal metabolic rate (BMR) from a variety of human endurance events, including triathlons and the Tour de France, and then added data from adults who ran 250 km per week for 20 weeks.
Study co-author and Duke University professor Herman Pontzer told Today’s Parent, “Every mother who has gone through a pregnancy has experienced that effort themselves. Pregnancy is the longest-duration, highest-energy-expenditure thing that humans can do. Mothers probably aren’t surprised by this.”
But can the expenditure of other kinds of energy during pregnancy reach a point where it becomes dangerous? Do excess levels of stress during pregnancy, for example, carry over in negative ways that can impact the long-term health of a newborn?
Potentially long-lasting effects
Researchers at The University of Western Australia (UWA) drew information from a multi-generational study known as the Raine Study, which included almost 3,000 women in their 18th week of pregnancy between May 1989 and November 1991.
The group from UWA partnered with researchers from the University of Copenhagen in Denmark, The University of Sydney and The University of Melbourne to focus on 643 20-year-old young men who had experienced at least one stressful event during the period of early gestation (zero to 18 weeks). All of these subjects underwent a testicular ultrasound exam and also submitted blood and semen samples for further study.
According to a UWA press release, the researchers determined that those men demonstrated lower testosterone concentrations and impaired sperm quality than other men who were not exposed to stressful events in the same gestational period or who had been exposed during the 18- to 34-week gestational period.
The mothers included in the study had filled out questionnaires at the 18- and 34-week gestation periods, answering questions about stressful events including those related to separation or divorce or marital problems, involuntary job loss (including their partner’s), moving home, death of a friend or close relative, money problems, and pregnancy concerns.
Researchers determined that 63 percent of the male subjects had been exposed to at least one stressful event in the 0- to 18-week gestation period. Those who had been thus exposed showed fewer sperm that could swim well (motility) as well as lower total sperm counts. Researchers adjusted their reading of these metrics to account for influencing factors such as socio-economic status, the mothers’ body mass index, and whether the mother had previously given birth.
Putting it all in perspective
Professor Roger Hart, from UWA’s Medical School and medical director of the Fertility Specialists of Western Australia IVF unit, noted that the researchers had merely made a connection between stressful life events in early pregnancy and reduced sperm quality and testosterone concentrations in offspring; they did not conclude that one without question caused the other.
“We 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 an 11 per cent reduction in testosterone levels compared to those men who were not exposed to any stressful life event during that period,” he said.
Hart added that these findings suggest that mothers who are exposed to stressful events during early pregnancy might pass along adverse fertility effects to their male offspring. He also said that a mother’s exposure to stress in early pregnancy was not likely to be the only cause of male infertility, but when combined with other factors, it could contribute to additional risk.
These factors include smoking, excessive alcohol intake, being obese or overweight, exposure to chemicals in the environment, and high blood pressure.
Hart offered this additional perspective: “[T]he association between exposure to stressful life events and reduction in sperm counts was not as strong as the association between maternal smoking and subsequent sperm counts, as this was associated with a 50 per cent reduction in sperm number.”
While potential negative consequences of maternal stress during early pregnancy might not be able to be mitigated by proactive storing of assets, it is important to note the “snowball” effect that various factors can play in impacting male fertility. Legacy’s at-home semen analysis can provide you with valuable information concerning the state of your fertility.