More than a quarter of pregnancy losses could be linked to the father’s health, research suggests.
A miscarriage is defined as losing a pregnancy in the first 23 weeks. Beyond that, the loss is considered a stillbirth.
Many factors likely contribute to a pregnancy loss, with the cause not usually being identified. Miscarriages and stillbirths are known to be more common, however, among women who are older, smoke or obese.
To learn more, scientists from Stanford University in California analysed nearly a million pregnancies that arose in the US between 2009 and 2016.
Results suggest in 27% of the cases where the father had metabolic syndrome, the woman endured a miscarriage, stillbirth or ectopic pregnancy; when a fertilised egg implants outside the womb.
This is compared to a 17% risk when the father did not have the condition.
Metabolic syndrome is the medical term for the combination of diabetes, high blood pressure and obesity, putting a patient at risk of heart disease and strokes.
“It’s been known for some time the health of mothers has an impact on the developing foetus and events at the time of birth,” said lead author Dr Michael Eisenberg.
“This is the first study to suggest pregnancies sired by men with increasing numbers of medical conditions are at higher risk of ending in miscarriage, ectopic pregnancy or stillbirth.
“While this study cannot prove poor paternal health is a cause of pregnancy loss, it shows there is an association.
“The clinical implications of these findings are pre-conception counselling should not forget the father, as his health may have an important impact on the pregnancy.”
Most miscarriages occur before a woman knows she is pregnant. Among those who are aware they are expecting, around one in eight pregnancies end in miscarriage.
Losing three or more pregnancies in a row, defined as recurrent miscarriages, affects around one in 100 women.
Watch: Meghan Markle makes first appearance since miscarriage
The Stanford scientists analysed data from US insurance claims, covering more than 958,000 pregnancies.
The results, published in the journal Human Reproduction, revealed just under a quarter (23.3%) of the fathers-to-be had at least one component of metabolic syndrome prior to conception.
Overall, 22% of the pregnancies were ectopic, or ended in a miscarriage or stillbirth. Ectopic pregnancies cannot be saved, with the misplaced fertilised egg usually having to be removed via medication or surgery.
As the scientists expected, pregnancy losses were more common among the older mothers and those with health issues.
The results among the fathers-to-be were more surprising, however.
“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,” said Dr Eisenberg.
Pregnancy loss also became more common as the men aged.
The results remained the same after the scientists accounted for other factors that can influence a pregnancy’s outcome, like the mother’s age, weight and smoking status.
Father’s health ‘may alter how the placenta functions’
While miscarriages rarely have an obvious cause, abnormal chromosomes are often to blame, with a baby being unable to develop if it has too many or not enough. Chromosomes contain tightly-packaged bundles of a person’s DNA.
“We hypothesise the father’s health and lifestyle could adversely affect the genetic make-up and expression in the sperm, and this may alter how well the placenta functions,” said Dr Eisenberg.
“If the placenta isn’t working properly then this could lead to the pregnancy losses we observed.
“For instance, we know already paternal smoking and diet can affect sperm quality.”
The scientists pointed out their method of analysis meant pregnancy losses that did not result in a medical claim were unaccounted for, like some early miscarriages.
Nevertheless, the frequency of miscarriages, stillbirths and ectopic pregnancies observed in the study were similar to estimates for the general US population, they added.
As the results are based on privately insured parents, the findings may not apply to other members of the population, like those of a lower sociodemographic status.
“We now need confirmatory studies,” said Dr Eisenberg.
“Hopefully, paternal health can be more integrated into future studies.
“In addition, investigations that target the possible mechanisms will help to better understand the associations we found.”
Professor Andrew Prentice from the London School of Hygiene & Tropical Medicine added: “This is an impressive analysis based on a very large sample size and with careful adjustments for confounders.
“It shows a clear link between a father’s metabolic health prior to the conception of the baby and the chances that the pregnancy will produce a healthy baby.
“For couples planning a pregnancy, maintaining a healthy weight and varied diet, quitting smoking and moderating alcohol intake, are probably just as important for fathers as for mothers.”
Watch: Gemma Collins opens up about her third miscarriage