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STANFORD, Calif. — While most of the focus during pregnancy is on the mother-to-be and her health, a new study finds that dad’s health might be just as important to a successful delivery. A researcher from Stanford University School of Medicine says a review of nearly one million pregnancies reveals an unhealthy father can lead to child loss.

Associate Professor Michael Eisenberg says more than a quarter of pregnancies may end in miscarriage or stillbirth if the father-to-be is obese, has diabetes, high blood pressure, or high cholesterol levels. The study also finds that if a father has a form of metabolic syndrome, there is an increased risk of the mother losing the fetus.

Greater danger as health declines

The risk of pregnancy loss increased by 10 percent, 15 percent, and 19 percent respectively for men with one, two, or three of these conditions. The chance of miscarriage or stillbirth also increased with the age of the father.

“It’s been known for some time that the health of mothers has an impact on the developing fetus and events at the time of birth,” Prof. Eisenberg says in a media release. “This is the first study to suggest that pregnancies sired by men with increasing numbers of medical conditions are at higher risk of ending in miscarriage, ectopic pregnancy or stillbirth.”

Study authors analyzed data from U.S. insurance claims covering 958,804 pregnancies as well as patient information regarding metabolic syndrome, chronic obstructive pulmonary disease (COPD), depression, and heart disease.

Mom and dad both play a vital role in pregnancy

The data reveals that 4.6 percent of men were over 45 years-old at the time of their partner’s pregnancy. Over 23 percent of the fathers-to-be had at least one condition tied to metabolic syndrome. Between 2009 and 2016, 22 percent of mothers lost their child due to an ectopic pregnancy (when the fertilized egg attaches outside the womb), miscarriage, or stillbirth.

Pregnancy losses increased with the mother’s age and the number of medical conditions she had, but the link between the father’s health and pregnancy loss remained as well.

“In the group of men we studied, the risk of losing the pregnancy was 17% in couples where the father had no components of the metabolic syndrome but increased to 21% in couples where the father has one metabolic syndrome component, 23% where he has two, and 27% where he has three or more,” Eisenberg reports.

“While this study cannot prove that poor paternal health is a cause of pregnancy loss, it shows there is an association. The clinical implications of these findings are that pre-conception counseling should not forget the father, as his health may have an important impact on the pregnancy.”

Dad’s diet may impact pregnancy

Eisenberg theorizes the father’s health and lifestyle choices could have negative impacts on the genetic makeup of his sperm. This may alter how well the placenta functions during pregnancy.

“If the placenta isn’t working properly then this could lead to the pregnancy losses that we observed; for instance, we know already that paternal smoking and diet can affect sperm quality.”

The findings appear in the journal Human Reproduction.

SWNS writer Joe Morgan contributed to this report.

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