Boys who are born small for their gestational age have an increased risk of fertility problems in adulthood, a Danish study published today (13 December 2019) has claimed.
The study, which followed 5,594 men and 5,342 women born in Denmark between 1984 and 1987 until the end of 2017, found that men who had been born small – in the bottom 10% – for gestational age had a 55% increased risk of infertility compared to men born within the appropriate weight range for gestational age.
The research team from Aarhus University said of those born small, 8.3% had been diagnosed or were being treated for infertility by the end of 2017 compared to 5.7% of men born with the appropriate weight.
There was no link between gestational age and infertility in women.
Previous research suggested a link between restricted growth of the foetus in the womb and a two to three times increased risk of penis and testicular problems in boys, particularly hypospadias, cryptorchidism and testicular cancer.
When the research team excluded men born with hypospadias or cryptorchidism for this study, which is published in Human Reproduction, the link between being born small for gestational age and infertility weakened.
They found a statistically non-significant 37% increased risk of infertility among the remaining men, with 7.3% of men born small for gestational age being infertile compared to 5.6% of men born with the appropriate weight.
Ms Anne Thorsted, who carried out the study when she was part of a research group from the Department of Public Health at Aarhus University, said: “This may indicate that part of the association between gestational weight and infertility is mediated by the effects of hypospadias and cryptorchidism, which is known to be related to later risk of infertility.”
She said it was not yet clear what the potential mechanisms could be for the link between birth weight and infertility.
Thorsted A, Laurdisen J, Høyer B et al. Birth weight for gestational age and the risk of infertility: a Danish cohort study. Human Reproduction. 13 December 2019; doi:10.1093/humrep/dez232.
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