When it comes to planning pregnancy, preconception counseling on diet and exercise is almost exclusively directed at the woman. A new study that included almost one million pregnancies suggests that way of thinking may be outdated, and perhaps men need to be in on those prepregnancy healthy lifestyle discussions, too.

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A retrospective study that looked at pregnancies between 2009 and 2016 published December 18, 2020, in Human Reproduction found that if a father-to-be has three or more medical conditions that are part of metabolic syndrome: obesity, diabetes, high blood pressure, or high cholesterol, the risk for losing a pregnancy was 27 percent compared with 10 percent for men who had no medical conditions.

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Preconception counseling, things like prenatal vitamins and living a healthy lifestyle, has only focused on women. This is the first study to show an association between the preconception paternal health and pregnancy loss, says Michael Eisenberg, MD, associate professor of urology at Stanford University School of Medicine in Palo Alto, California, and lead author of the study.

Eisenberg and his team analyzed data from U.S. insurance claims that covered 958,804 pregnancies between the years 2009 and 2016. Researchers evaluated the health of the father according to records of medical conditions, which included components of metabolic syndrome (obesity, diabetes, high blood pressure, and high cholesterol) as well as chronic obstructive pulmonary disease (COPD), depression, and heart disease.

The burden of chronic disease for all the men was calculated by reviewing their health history of heart failure, heart attack, diseases of the blood vessels, kidney and liver disease, cancer, stroke, and dementia.

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Calculations were adjusted to account for other factors that can impact pregnancy, including the mothers age, health, weight, and whether either parent was a smoker.

A total of 4.6 men in the study were over 45 years old and 23.3 had at least one component of metabolic syndrome prior to conception. Of the pregnancies included, there were 785,809 live births and 172,995 pregnancies lost to ectopic pregnancy, miscarriage, or stillbirth.

Investigators found that the more components of metabolic syndrome the father had, the higher the risk for a pregnancy loss.

The risk of pregnancy loss was:

The fact that the risk of an adverse event in pregnancy increased with each additional health component strengthens the findings of this study, says Chad Aaron Grotegut, MD, professor of obstetrics and gynecology at the Wake Forest School of Medicine and a maternal-fetal medicine specialist at Wake Forest Baptist Health, both in Winston-Salem, North Carolina. Dr. Grotegut was not involved in this research. I think that seeing that sort of dose response strengthens the argument that this may be a true finding, he says.

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Investigators also discovered that the risk of pregnancy losses increased with the mothers age and the number of medical conditions she had, but even after allowing for that, the association between the health of the father and pregnancy losses remained. The risk of losing a pregnancy also went up as the age of the father increased.

The authors do a good job of acknowledging there are some limitations to the study, says Grotegut. In research, anytime that youre going back and analyzing data that was collected for a different purpose, theres always a concern that certain data or conditions were either not recorded or not recorded correctly, he says.

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Other limitations are that the data included only people who were privately insured and employed, and the data didnt include race, substance abuse, or sociodemographic status such as education level or income, said the authors.

Although this study wasnt designed to uncover the why behind the association between paternal health and the risk of pregnancy loss, there is existing research that offers a few clues. There have been some studies to suggest that the sperm in men that are older, who smoke or who have obesity may have abnormal epigenetic signatures in their sperm, says Eisenberg.

Epigenetics is the study of how your behaviors and environment can cause changes that impact the way your genes function, according to the Centers for Disease Control and Prevention (CDC). Epigenetic changes are reversible and do not change your DNA sequence, but they can affect how your body reads a DNA sequence.

These epigenetic changes dont change the DNA code, but they change how well and how efficiently that DNA is expressed, he explains.

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Its possible that these chronic health conditions of the men lead to poor epigenetic signatures of the sperm, says Eisenberg. If the sperm DNA cant be expressed efficiently or perfectly, that may lead to a poor embryo or a poor placenta that then can lead to this adverse pregnancy trajectory where its more likely to end, he says.

Research has shown that a pregnant womans environment and behavior during pregnancy, for example whether or not she eats a healthy diet, can change the babys epigenetics, according to the CDC.

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Eisenberg and his colleagues published a 2018 study in The BMJ that used data from 40.5 million live births from a U.S. national data-sharing program to examine the impact, if any, of the fathers age.

After controlling for factors such as education level, marital status, smoking history, access to healthcare and the mothers age, investigators found that older fathers were linked to increased risks at birth, including low birth weight and seizures. The infants born to older fathers were more likely to require ventilation and neonatal intensive care as well.

Although there arent any human studies to date, a study published in the Proceedings of the National Academy of Scienceslooked at mules, which have horse mothers and donkey fathers, and hinnies, which have horse fathers and donkey mothers. Investigators found thatgenes from the animals fatherswere predominant in the placenta.

The placenta is the organ that gives the fetus nourishment and oxygen and filters out waste products through the umbilical cord.

One avenue for further research would drill down deeper to examine the individual health of the fathers-to-be, says Eisenberg. For example, if a person has diabetes, lets look at how tightly theyre controlling their blood sugars and how they are doing it, whether that be through diet and exercise or medication. We could discover that what were seeing as far as increased risk in pregnancy could be the disease itself, but it could also be the treatment for the disease, he says.

Replicating the study and looking at individuals with more detail is really crucial to understanding what is going on, adds Eisenberg.

This is only one study, and at this point it hasnt been proved that the fathers health causes the increased risk in pregnancy, says Eisenberg. That being said, the advice that we would give a man would not be harmful, even if further studies dont prove causation, he says.

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Men should be mindful of their diet, to exercise, maintain a healthy body weight, and check in with their primary care doctor to make sure that theyre in good health, says Eisenberg. I think thats reasonable, its going to benefit their health, and this data suggests that it would hopefully benefit the pregnancy as well, he says. Maybe this could be an extra carrot to get people, specifically men, to adhere to some of those recommendations, he adds.

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Health of Father-to-Be Linked to Pregnancy Loss Risk - Everyday Health