Sperm damage: Decoding link between repeated miscarriages and men

LONDON: Repeated miscarriages are often attributed to a problem in the affected women who are then made to undergo many tests to determine the root cause. However, a new study has found that recurrent pregnancy loss (RPL) may also occur due to sperm DNA damage in the male partner. The study was presented at the ENDO 2019: The Endocrine Society Annual Meeting.

Recurrent pregnancy loss is defined as the consecutive loss of three or more pregnancies before 20 weeks gestation. It occurs in 1-2% of couples, and about half of cases are unexplained. Channa Jayasena, M.D., Ph.D., of Imperial College London in London, U.K., and colleagues conducted the study to assess whether male partners of women with RPL may have an increased risk of sperm DNA damage, which is known to impair fertility.

"Affected women undergo many tests to determine the cause, but many cases have no identified cause," said Dr. Jayasena. Male partners of women with RPL do not routinely undergo an assessment to see if they play a role. She further adds that, however, we know that sperm play an important role in the formation of the placenta, which is critical for the survival of an unborn baby.

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For the study, the researchers compared 50 healthy men whose partners had not experienced miscarriages with 63 men whose partners were affected by RPL. They measured levels of sex hormones such as testosterone, the number, and behavior of sperm using a microscope, and further molecular tests. They also measured the level of damage to sperm DNA, and level of a chemical entity called reactive oxygen species, which can damage cells such as sperm in the semen of men.

The RPL partners (females) were a little older (average age 37 vs 30 years) and had a slightly higher body mass index (27.6 vs 24.8 kg/m²) compared with controls. Rates of smoking and alcohol consumption were similar in both groups.

Key findings of the study include:

• About 3.4% of sperm had normal morphology among the males of couples whose partners suffered recurrent miscarriages, compared with 4.5% of controls' sperm, and DNA damage was more than doubled in RPL male partners (mean DNA fragmentation index [DFI], 16.3) compared with controls (DFI, 7.4).


• The greatest difference between the groups was in seminal reactive oxygen species levels, which were fourfold higher in RPL male partners compared with controls (9.3 vs 2.3 RLU/sec/10⁶ sperm).


• The RPL male partners also had slightly lower but nonsignificant mean serum morning testosterone than controls (15.8 vs 17.9 nmol/L).

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"Our study suggests that it may be useful to investigate if male partners of women with RPL have abnormalities in their reproductive function," Jayasena said. "It also opens up a new potential 'drug target'; it may be possible to design future drugs to stop sperm DNA damage to treat couples with RPL and reduce the risk of miscarriage."