Women have always been cautioned about biological clocks. As a woman goes from her 20s to her 30s to her 40s without having kids, she’s likely to hear many people advise her about the pregnancy risks, but recently, a new research has revealed that it’s just not the female fertility clock that’s ticking.
The study from the USA in IVF couples shows quite plainly that live birth result is certainly affected by the age of the male partner and that in certain younger female age groups, where the effect of age is less important, the chances of live birth can be significantly decreased if the man's age is increasing.
“Our study found an independent effect of male age on the cumulative incidence of live birth,” said investigator Laura Dodge from Beth Israel Deaconess Medical Centre and Harvard Medical School, Boston, USA.
The study was a scrutiny of all IVF cycles performed at a large IVF centre in the Boston region between 2000 and 2014, a total of almost 19,000 cycles performed in 7,753 couples. The female partners in these cycles were classified according to four age bands: under 30, 30-35 years, 35-40 years, and 40-42. Men were also labelled into these same four age bands, with an additional group of 42 and over.
As expected, the aggregate live birth rate (measured from up to six cycles of treatment) was lowermost in those couples where the female partner was in the 40-42 age band, and in this group the age of the male partner had no effect, showing the chief harmful effect of female age. However, within the other bands of female age, the cumulative frequency of live birth was majorly affected by male partner age and was found to decrease as the man grew older.
For example, in couples with a female partner who was under 30, a male partner aged 40-42 was linked with a considerable lower cumulative birth rate (46%) than a male partner aged between 30-35 (73%). Likewise, in couples who had a female partner aged 35-40 years live birth rates were higher with a younger man with an older male partner.
“Generally,” explained Dodge, “we saw no significant decline in cumulative live birth when women had a male partner the same age or younger. 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% relative improvement in cumulative incidence of live birth when compared to women whose partner is 30-35 - from 54% to 70%.”
“Where we see significant decreases in the cumulative incidence of live birth is among women with male partners in the older age bands. For women age 30-35 having a partner who is older than they are is associated with approximately 11% relative decreases in cumulative incidence of live birth - from 70% to 64% - when compared to having a male partner within their same age band.”
Commenting on the results, Dodge noted that in natural conceptions increasing male age is associated with a decreased incidence of pregnancy, increased time to pregnancy, and increased risk of miscarriage. The mechanisms, she added, are unclear but may include impaired semen parameters, increased DNA damage in sperm, and epigenetic alterations in sperm that affect fertilisation, implantation, or embryo development.
“However,” said Dodge, “both the results of this study and prior work show that female age has a larger effect on fertility than male age.
While the effect of female age on fertility is overwhelmingly due to increased rates of chromosomal abnormality, the proposed mechanisms in the effect of male age on pregnancy are subtler. When we looked at the effect of female age alone, we saw a 46% relative decrease from ages under 30 to 40-42, but when we looked at male age alone, we saw a 20% relative decrease over the same age span.”
Can men with younger female partners take any action regarding balancing of this age effect in IVF? “It’s hard to say without knowing the precise mechanisms involved,” said Dodge.
“Most preconception advice for men focuses on semen quality, though studies suggest that this likely cannot fully ameliorate the effects of male reproductive ageing. So, in the absence of clear evidence of the mechanisms, the best preconception advice we can offer is to maintain a healthy lifestyle.” The study will be presented at the 33rd Annual Meeting of ESHRE in Geneva.