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 Centre and Harvard Medical School, the incidence of live birth declines significantly as men grow older.

The study analysed 19,000 in-vitro fertilisation (IVF) cycles in 7,753 couples at an IVF centre 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, women under 30 had a 73% success rate with IVF if their partners were between 30 and 35.