Scientists have pinpointed specific maternal genetic variants that raise the odds of producing aneuploid embryos—those with the wrong number of chromosomes—a key driver of early pregnancy loss. The discovery, published in Nature in January 2026, marks the first time researchers have linked common variations in a mother’s DNA to the risk of chromosome‑number errors that can end a pregnancy before it is clinically recognized.
About half of first‑trimester miscarriages are caused by aneuploidy, a condition in which cells carry too many or too few chromosomes — a fact documented in medical literature (PMCID: PMC4736891). The problem is far more common in egg cells than in sperm, and the proportion of aneuploid eggs climbs sharply as women age.
How the study was built
Researchers examined genetic testing data from more than 139,000 embryos created through in‑vitro fertilization (IVF). The cohort included 22,850 mothers ranging from roughly 20 to 56 years old, with an average age of 36 years. By tracing each embryo’s haplotype, the team identified 3.8 million crossover events and 92,485 aneuploid chromosomes, allowing a direct comparison of genetic variation and chromosomal outcomes.
“We previously didn’t have any remarkably well‑characterized associations between genetic variation in the mother’s genome and risk of producing eggs with aneuploidy,” said Rajiv McCoy, an associate professor of biology at Johns Hopkins University, speaking to Live Science.
Key genetic findings
Genome‑wide association studies highlighted two genes with the strongest links to aneuploidy risk. Specific alleles of SMC1B, a meiotic cohesin that holds sister chromatids together, showed a clear association. A second signal emerged from variants in C14orf39, a component of the synaptonemal complex that facilitates chromosome pairing during meiosis.
The investigators also measured crossover count—the number of DNA exchanges that occur when homologous chromosomes swap segments. Embryos that were aneuploid displayed fewer crossovers, confirming earlier work that linked insufficient recombination to segregation errors (Wiley). “The same machinery that’s influencing recombination is the machinery that’s influencing risk of producing these aneuploidies,” McCoy explained.
Implications for patients and research
While the identified variants each explain only a modest fraction of an individual’s overall risk, the findings open a path toward more precise risk models. “That doesn’t mean that it’s not possible in the future to get better predictions of people’s risk,” McCoy said. “And this provides one clue as to what we should be looking for.”
Miscarriage remains common: “About 10% to 20% of clinically recognized pregnancies end in miscarriage,” McCoy noted, adding that roughly half of all conceptions are lost before birth, many before a woman knows she is pregnant.
For now, the study is not ready for clinical use. The authors stress that translating these genetic signals into diagnostic tools will require larger, diverse cohorts and functional experiments to confirm how the variants alter protein function.
What’s next?
The research team plans to expand the analysis to include paternal genetic contributions and to explore how environmental factors interact with the identified variants. Follow‑up studies will also investigate whether targeted interventions—such as optimizing IVF protocols for women carrying high‑risk alleles—can reduce the incidence of aneuploid embryos.
As more data accumulate, clinicians and patients can look forward to evidence‑based guidance on how maternal genetics may influence reproductive outcomes.
Disclaimer: This article provides general information and does not constitute medical advice. Readers should consult qualified healthcare professionals for personal health decisions.
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