Study Links Maternal Genes to Pregnancy Loss Risk for First Time

A groundbreaking study has established a link between maternal genetic variants and the risk of pregnancy loss, particularly due to chromosomal abnormalities. Published in the journal Nature, this research reveals that aneuploidy, a condition where embryos have an abnormal number of chromosomes, is a significant cause of pregnancy loss, especially during the first trimester. Approximately half of early pregnancy losses are attributed to this condition.

Aneuploidy primarily affects egg cells rather than sperm cells, and its prevalence increases as women age. This condition can lead to infertility and genetic disorders in offspring, which may result in severe disability or even death. Despite its impact, the specific genetic factors contributing to the likelihood of producing aneuploid eggs have remained largely uncharted.

Research led by Rajiv McCoy, an associate professor of biology at Johns Hopkins University, aimed to fill this knowledge gap. The team analyzed clinical genetic testing data from over 139,000 embryos created for in vitro fertilization (IVF), which included samples from 22,850 mothers aged between 20 and nearly 56 years, with an average age of approximately 36. This age is critical, as it marks a sharp increase in the risk of producing aneuploid embryos.

“We previously didn’t have any very well-characterized associations between genetic variation in the mother’s genome and risk of producing eggs with aneuploidy,” McCoy stated in an interview. The researchers conducted genome-wide association studies to identify statistical links between the genetic variants of the mothers and the incidence of aneuploid embryos.

The study identified significant associations with specific gene variants, particularly SMC1B, which encodes a protein essential for maintaining chromosome structure, and C14orf39, known to facilitate important interactions between chromosomes during cell division. The findings suggest that errors in a process called “crossover recombination,” where chromosomes exchange segments of DNA during egg or sperm formation, are linked to aneuploidy.

McCoy’s team found that the number of DNA exchanges during crossover recombination was lower in aneuploid embryos, supporting earlier findings that errors in this process contribute to increased rates of aneuploidy. Notably, the genetic variants associated with aneuploidy risk were also linked to these recombination processes. “The same machinery that’s influencing recombination is the machinery that’s influencing risk of producing these aneuploidies,” McCoy explained.

The implications of this research extend beyond understanding genetic risks. It highlights the shared genetic basis of crossover recombination and aneuploidy, underscoring the critical role of crossovers in ensuring the correct number of chromosomes in viable eggs. McCoy emphasizes the significance of these insights, stating that “the value of this study is more fundamental,” as it aids in understanding human biology.

Miscarriage is a common occurrence, with estimates suggesting that 10% to 20% of clinically recognized pregnancies end in loss. In reality, around half of all conceptions may not result in a live birth, particularly early in development. Understanding the genetic factors contributing to aneuploidy could pave the way for improved diagnostics and therapies aimed at reducing pregnancy loss.

While the findings cannot yet be applied to patient care, they provide a foundation for future research. McCoy notes, “It’s too early for these findings to be used in clinical settings, but they offer clues for better predictions of individual risks.” Ultimately, this study not only sheds light on the genetic underpinnings of pregnancy loss but also contributes to a broader understanding of human reproductive health.

As research continues, the insights gained from this study could lead to advancements in fertility treatments and a deeper understanding of the mechanisms underlying pregnancy loss, helping countless individuals and families in their reproductive journeys.