• Marie Otsuka

PSA: Men who are born underweight may struggle with fertility problems


According to a recently published Danish study, men who were born underweight are more likely to experience difficulties when trying to conceive with their partner. Why do men’s weight at their time of birth affect their subsequent fertility? Does this study also apply to Asians? Read on to find out more!

Men born under 6.6lbs are 55% more likely to be infertile

The study involved 5594 men and 5342 women born between 1984 and 1987, and researchers from that men born under 6.6lbs (~3kg) had a 55% increased risk of infertility as adults. Interestingly, there was no link between women’s weight at their time of birth, and their subsequent fertility.

All in all, approximately 5.7% of men are expected to suffer from infertility in a normal population, but if you look specifically at a sample of men born underweight, 8.3% of them would suffer from infertility.

Why do men who are born underweight grapple with infertility?

There are several reasons as to why being born underweight may lead to problems with infertility further down the road. Firstly, a baby being born underweight indicates a “suboptimal growth environment for the foetus”, which could also be detrimental to the development of sperm production and reproductive organs.

On top of that, the researchers of the study point out that the mother's health and lifestyle during pregnancy could affect both foetal growth and the development of reproductive functions. For instance, if a mother smokes during her pregnancy, this could potentially stunt the growth of her foetus, and impact the development of their reproductive functions as well.

Does this study apply to Asians as well?

This particular study utilised data from a Danish birth cohort, but are the findings applicable to Asians and Singaporeans as well?

If you look at it from a theoretical perspective, all signs point to yes. The science behind it stays the same - babies who are born underweight are probably subject to suboptimal environments while they were developing, and this could impact the development of their sperm and/or reproductive organs.

That said, Asian babies tend to be smaller than Danish babies: Danish babies born at full term weigh between 2.5kg to 4.5kg, while the average weight of a Singaporean baby clocks in at between 2.5kg to 3.5 kg). Bearing this in mind, while the cut-off point for what’s defined “underweight” is 6.6lbs (~3kg) in Denmark, this may differ in Singapore.

Think that you or your partner may be suffering from infertility? Regardless of whether it’s due to your birth weight, or other factors, your best bet is to visit an ob-gyn and undergo a fertility test, so you can find out for sure.


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