Infants of older fathers are more likely to be less healthy at birth
Delaying fatherhood is associated with negative effects on both infants and mothers, suggests a US study published by The BMJ.
The researchers stress that the absolute risks remain low, but say their findings emphasise the importance of including men in preconception care–and the need to further investigate the public health implications of rising paternal age within developed countries.
For years women have been encouraged not to put off having children until their late thirties and forties because it will mean added risks for themselves and their babies, and now it appears that the age of the father also has an impact.
Few previous studies have looked at the impact of the age of fathers, and those that have have focused mainly on the risk of congenital diseases in infants.
In the latest study, researchers at Stanford University in California accessed data on all 40,529,905 live births that took place in the US between 2007 and 2016 to look at the impact of paternal age on a range of outcomes for the infant and the mother.
They 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 healthcare support after delivery, such as assisted ventilation, admission to neonatal intensive care, or antibiotics.
After adjusting for age of the mother, maternal smoking, race, education, and number of prenatal visits, children of fathers aged 45 years or more were born 0.12 weeks earlier and with a 14% higher odds of being premature (less than 37 weeks) compared to those whose fathers were aged 25 to 34 years.
Children of fathers aged 45 years or more were born 20.2g lighter and had a 14% greater risk of low birth weight (less than 2500g) than infants born to younger fathers.
Infants with fathers aged 45 years or more also had a 14% higher odds of being admitted to a neonatal intensive care unit and a 18% higher odds of having seizures, compared with infants with fathers aged 25 to 34 years.
If the father was aged 55 years or older, newborns also tended to score less well on the Apgar test–a test used to quickly assess the health of a child at birth.
The risk of gestational diabetes for pregnant women also increased in line with the age of the father, with women carrying the child of a man aged 55 years or older having a 34% higher odds of gestational diabetes.
The researchers estimate that around 13% of premature births and 18% of gestational diabetes in pregnancies associated with older fathers were attributable to the advanced age of the father, and suggest that changes in the sperm of older men might explain their findings.
The researchers stress that this is an observational study, so no firm conclusions can be drawn about cause and effect. And they cannot rule out the possibility that despite attempts to adjust and account for potential maternal factors, some unmeasured effects from older fathers being associated with older mothers may remain.
They also point out that the overall risk of these outcomes likely still remains low, but conclude that advanced paternal age is associated with negative effects on both mothers and offspring.
“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 write.
In the US, the number of first births to women older than 35 years has risen by about 2% annually since the 1970s, and the percentage of all births in the US to fathers aged more than 40 has doubled to 9% over the same period.
These findings underline the importance of including men in preconception healthcare, writes Hilary Brown, Assistant Professor at the University of Toronto, in a linked editorial.
She agrees that this observed association might not be causal, and points out that the relative and absolute risks were low. But she says changes to public health messaging and primary care are needed “to promote awareness of the role of male factors, including paternal age, in perinatal outcomes.”
See the related editorial at https://www.bmj.com/content/363/bmj.k4466
Reference: BMJ 2018; 363 doi: https://doi.org/10.1136/bmj.k4372 (Published 31 October 2018) Cite: BMJ 2018;363:k4372
1 November 2018.