Sperm with DNA damage might be the true cause of repeated miscarriages

New guidelines say testing sperm for DNA damage could help explain recurrent pregnancy losses

In the summer of 2024 fertility doctor Carrie Bedient sat across from a young couple and braced herself for a difficult conversation. The man and woman, both 32 years old, had been seeking medical help at her clinic to have a baby for the previous five years. But multiple rounds of in vitro fertilization (IVF) treatment had failed. By the time Bedient met with them to discuss the next steps, they had been through repeated miscarriages, failed embryo transfers and another kind of early pregnancy loss known as a chemical pregnancy.

Bedient, a reproductive endocrinologist at the Fertility Center of Las Vegas, had already ordered the usual battery of tests, including bloodwork, sperm count and motility tests and uterine anatomy exams. So she turned to what was then a more controversial idea: testing for DNA damage in the man’s sperm. He said yes.

By that point, a growing body of research had linked DNA fragmentation in sperm to an increased risk of miscarriage. But despite a test for this factor being available for some 15 years, it wasn’t commonly done—not least because doctors weren’t sure what people could do with the information. It was also unclear what caused the DNA damage in the first place; culprits ranged from environmental toxins to advanced paternal age to lifestyle factors, such as drug use and smoking. Plus, tests could cost up to $500 and weren't always covered by insurance.

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In the man’s case, the test results revealed a moderate level of DNA damage. Bedient gave him some frank advice on how to rehabilitate his sperm. “Hey, I need you to clean up everything you can,” she recalls telling him. He vowed to stop drinking alcohol, stop smoking, start exercising and take vitamin supplements—and it worked.

Six months later, the couple made another batch of embryos. “He completely turned everything around, and they’ve now got a beautiful baby boy,” Bedient says.

When a man starts infertility treatment, he typically undergoes a workup that analyzes the volume and concentration of his semen, the shape of his sperm and their ability to move. Yet the association of damaged sperm with miscarriage—in addition to newer research linking it to lower IVF live birth rates and poorer early embryo development —is pushing doctors to delve deeper into sperm health.

In its first update in 14 years, the American Society for Reproductive Medicine (ASRM) released new treatment guidelines for recurrent miscarriage, noting that testing for sperm DNA fragmentation “may be considered” in cases of multiple pregnancy losses.