New U.S. research has found that delaying fatherhood until later in life could have a negative effect on both children and mothers.
The new large-scale study by researchers at Stanford University looked at data on all 40,529,905 live births that took place in the U.S. between 2007 and 2016.
After taking into account factors such as the age of the mother, maternal smoking, race, education, and the number of prenatal visits, researchers found that as the age of the father increased, so did the risk of the infant being born prematurely, having a low birth weight, and requiring health-care support after delivery such as assisted ventilation, admission to neonatal intensive care, or antibiotics.
Published by The BMJ, the study showed that children of fathers aged 45 years or more were born 0.12 weeks earlier and had a 14 per cent higher risk of being premature (less than 37 weeks) compared to those whose fathers were aged 25 to 34 years.
These children were also born 20.2g lighter and had a 14 per cent higher risk of low birth weight (less than 2500g) than infants born to younger fathers. They also had a 14 per cent higher risk of being admitted to a neonatal intensive care unit and an 18 per cent higher risk of having seizures, compared to infants with fathers aged 25 to 34 years.
Newborns of fathers aged 55 years or older also tended to score less well on the Apgar test — a test used to assess the health of a child at birth.
The team found that not only did a father's age impact his children's health, it also appeared to affect the mother's health.
WATCH: Study reveals new dads are now at their oldest. Story continues after video.
The risk of gestational diabetes for pregnant women increased as the age of the father increased, with women pregnant with the child of a man aged 55 years or older having a 34 per cent higher odds of gestational diabetes.
Although women are often advised not to delay motherhood for too long because of the added health risks for themselves and their babies, the researchers estimated from the new study that around 13 per cent of premature births and 18 per cent of gestational diabetes in pregnancies were due to the advanced age of the father. They suggested that changes in the sperm of older men could be responsible.
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The team stressed that as this is an observational study, no firm conclusions can be drawn about cause and effect, and that the overall risk of these negative outcomes still remains low. However, they added that the new findings emphasize the importance of including men in preconception care.
"A significant number of these negative birth outcomes were estimated to be prevented if older fathers had elected to have children before the age of 45 years. The risks associated with advancing paternal age should be included in discussions regarding family planning and reproductive counselling," they concluded.