A large new study suggests that men who plan to be fathers should try to get themselves in shape first.
Researchers found that when fathers-to-be had health conditions like high blood pressure or obesity, the odds that their partner might experience miscarriage or stillbirth increased.
The findings do not prove that a father's health directly affects his partner's pregnancy, experts said. But given that men's health and lifestyle habits can affect sperm quality, it's plausible that dads make a difference in pregnancy outcomes.
"We do need more studies to figure out the mechanisms," said senior researcher Dr. Michael Eisenberg, director of male reproductive medicine and surgery at Stanford University School of Medicine in California.
In the meantime, he said, there's certainly no harm in encouraging men to eat healthfully, exercise and get any chronic health conditions under better control.
The findings, published online Dec. 18 in the journal Human Reproduction, are based on insurance records covering nearly 959,000 U.S. pregnancies. Almost 173,000 ended in a pregnancy loss -- a miscarriage, stillbirth or ectopic pregnancy (when a fertilized egg implants outside the uterus).
Eisenberg's team looked at whether fathers' health diagnoses before conception showed any correlation with the risk of pregnancy loss.
In fact, they did. In general, the study found, the risk of pregnancy loss inched up with the number of health issues a father-to-be had.
If a man had one component of metabolic syndrome, for instance, the risk of pregnancy loss rose 10%. If he had three or more components, it rose by 19%, the investigators found.
Metabolic syndrome is a collection of risk factors for heart disease and stroke. It includes obesity, high blood pressure, high cholesterol and type 2 diabetes.
Past studies have linked older age in the father to poorer pregnancy outcomes, possibly because sperm quality diminishes with age.
But, in this study, the findings were not explained by older age, Eisenberg said. At any age, poorer health in the father mattered.
Of course, men with more health conditions might have a partner who is in poorer health, too. But Eisenberg's team accounted for the health of moms-to-be, and it did not fully explain the findings on fathers' health.
Dr. Rahul Gupta is chief medical and health officer for the nonprofit March of Dimes. He said, "We've known that the family's health is important to the health of a child." One reason is because children learn diet, exercise and other lifestyle habits from the adults around them, he noted.
The new findings, according to Gupta, suggest that a father's influence begins as early as conception.
Exactly why is unclear. But, he said, past research has shown that genes from the father help form the placenta -- and pregnancy loss is often associated with problems with the placenta.
"This is a field of science that needs to be developed more," Gupta said.
For now, he agreed with Eisenberg that the health of dads-to-be should not be ignored.
"For a long time," Gupta noted, "we didn't think that way."
Women's health remains "paramount" when it comes to pregnancy outcomes, Eisenberg said. But, he added, fathers-to-be can only do themselves and their family good by taking their own health seriously, too.
The March of Dimes has more on pregnancy loss.
SOURCES: Michael Eisenberg, MD, associate professor, urology, and director, male reproductive medicine and surgery, Stanford University School of Medicine, Stanford, Calif.; Rahul Gupta, MD, MPH, MBA, chief medical and health officer, and senior vice president, March of Dimes, Arlington, Va.; Human Reproduction, Dec. 18, 2020, online