While scientists and doctors have long known that a woman's chances of having a child drop the older she gets, a new study suggests that a man's age can affect a couple's chances as well. According to a new study out of Beth Israel Deaconess Medical Center and Harvard Medical School, the incidence of live birth declines significantly as men grow older. The study analyzed 19,000 in-vitro fertilization cycles in 7,753 couples at an IVF center between 2000 and 2014, according to a press release from the European Study of Human Reproduction and Embryology. "Declining sperm quality certainly plays some role, but our work shows that this is not the whole picture," says the lead researcher. "We found similar results among couples with no documented male infertility, so something else is happening."
Researchers divided participants into four age groups: under 30, 30-35, 35-40, and 40-42. They found that the younger the man was on average, the better the woman's chances of successful birth. For example, the Guardian reports, women under 30 had a 73% success rate with IVF if their partners were between 30 and 35. Women in that same category whose partners were between 40 and 42 saw that number drop to 46%. Among women 35 to 40 years old whose partners were between 30 and 35, there was a 54% chance of live birth. That rose to 70% in men under 30. The research "may help women to encourage their male partners to get a move on," says an obstetrics professor not involved in the study. "This reminds us that it takes two to tango and it’s not just down to the age of the woman." (Older dads make for geekier sons.)