Research suggests men too have a 'biological clock' and the longer they put off fatherhood, the less likely they are to be able to have children.
Experts claim that women who have delayed starting a family are better off trying for a baby with a younger man as the chances of conception are higher, as sperm DNA can become damaged with age.
A new study by academics at the Beth Israel Deaconess Medical Center analysed the data of 7 753 couples who visited a fertility clinic in Boston between 2000 and 2014. Women were split into four age groups - under 30, 30-35 year-olds, 35-40 year-olds and those aged 40-42 – while men had the same categories in addition to an over 42s set.
Women in the eldest group had the lowest birth rates, with men’s age playing no part in this.
However, younger women’s birth rates appeared to be affected by the age of their male partner.
Results showed that men aged between 30 and 35 had an average birth rate of 73 percent with a woman aged 30 or younger, compared to an average birth rate of 46 percent for men aged 40 to 42.
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There was no impact when the woman was the same age as the man, however, some women did see stronger results from being with a younger man, with ladies aged between 35-40 around 70 percent more likely to have a baby with a man aged 30 or younger, compared to 54 percent with men aged between 30-35.
"Generally, we saw no significant decline in cumulative live birth when women had a male partner the same age or younger," lead researcher Dr Laura Dodge said.
And added: "However, women aged 35–40 did significantly benefit from having a male partner who is under age 30, in that they see a nearly 30 percent relative improvement in cumulative incidence of live birth when compared to women whose partner is 30–35 – from 54 per cent to 70 per cent."
While she noted there was little men can do to change the impact of ageing on their sperm, she did suggest following a healthy diet.
"Declining sperm quality certainly plays some role, but our work shows that this is not the whole picture.
"We found similar results among couples with no documented male infertility, so something else is happening," Dr Dodge added.
The full study was presented at the European Society of Human Reproduction and Embryology meeting in Geneva on 4 July 2017.
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