August 31, 2021 – According to a recent study, men over 50 have a lower chance of having a baby through in vitro fertilization (IVF).
The study, published in Acta Obstetricia et Gynecologica Scandinavica, comes as delayed parenting becomes more common. According to a 2017 study, the median age of first-time fathers in the U.S. rose from 27 in 1975 to 31 in 2015. The median age of first-time mothers rose from 21 in 1970 to 27 in 2019, according to data from the CDC. Conception data in England and Wales found that 15% of babies born in 2016 had a father older than 40 years old.
While a woman’s chance of having a baby through IVF is known to decrease with age, the influence of a man’s age is less clear, the researchers in the new study write.
For the study, the researchers looked at data on the number of times couples had a baby after IVF using a fresh, unfrozen embryo formed from the couple’s own eggs or sperm between December 2009 and August 2018, London. Although the center performed more than 24,000 IVF cycles in total during that time, the researchers analyzed only about 5,000 that met their criteria.
Overall, couples had a baby after about 40% of the 5,000 IVF cycles. When the researchers analyzed the results for fathers in different age groups, they found that the rate of couples having babies after an IVF cycle decreased with the age of the father. More specifically, it was almost 50% for men under 35, 41% for men 36 to 40 years old, about 35% for men 41 to 45 years old, and 32% for men 46 to 50 years old. Men older than 50 had a significantly lower chance of having a baby – 30%.
The rate of clinical pregnancies, that is, doctors could detect a baby’s heartbeat between 6 and 7 weeks of pregnancy, also decreased with the age of the father. Couples with a father under 35 years of age had a clinical pregnancy rate of 50% of the cycles, while couples with a father over 50 years of age had a clinical pregnancy rate of 30%. However, the researchers said the age of the fathers doesn’t seem to affect the risk of miscarriage.
It’s not surprising that older men showed differences in reproductive outcomes after IVF, says urologist Bobby B. Najari, MD, director of male infertility at NYU Langone in New York City. As men get older, the DNA in their sperm is more likely to break, which can lead to a lower chance of conception and a higher risk of miscarriage. This can be a problem whether or not a couple are using IVF to try to have a baby.
The men over 50 involved in the current study, Najari noted, had a higher rate of intracytoplasmic sperm injection (ICSI), a procedure that is added to traditional IVF in which the sperm are injected directly into the egg rather than to combine them. Doctors usually recommend this procedure to men with lower sperm counts, which leads Najari to wonder if the group of couples were already less likely to have a baby regardless of their age.
Since the researchers performed their analysis per IVF cycle, “there could be the same pair over and over again in the data set,” he says, which could distort the results. If fewer men over the age of 50 performed more IVF cycles, “outliers may have a greater impact on outcomes”.
Previous studies have linked the age of fathers to adverse health outcomes after having a child. A 2009 study published in PLOS Medicine found that children with older fathers were associated with impaired central nervous system functions during childhood and childhood. Another study published in 2012 found that a 40-year-old father was twice as likely as a 20-year-old father to have a child with schizophrenia or autism spectrum disorder. This is because the risk of new genetic mutations in the father’s sperm increases with age, the researchers said.
Doctors already recommend speaking to older men who want to have children about the risk of schizophrenia, autism, and other negative health outcomes, says Najari. The new study now shows that as would-be fathers get older, they may be less likely to have a baby through IVF.
More studies are needed to investigate why older fathers’ age is linked to lower birth rates and clinical pregnancy rates, but does not affect miscarriage rates, the new study researchers said.
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