A recent study has uncovered genetic factors linked to chromosomal issues that can lead to pregnancy loss. About half of early pregnancy losses happen due to a condition called aneuploidy, where cells have too many or too few chromosomes. This issue is more prevalent in egg cells than in sperm, especially as a woman ages. Studies show that the risk of producing aneuploid eggs increases significantly after age 35.
Rajiv McCoy, an associate professor at Johns Hopkins University, notes that the relationship between a mother’s genetics and aneuploidy in embryos hasn’t been well understood. His team explored this by analyzing genetic data from over 139,000 embryos created during in vitro fertilization (IVF). Their study included mothers aged 20 to 56, with an average age of 36.
During the research, they found connections between genetic variants in mothers and the likelihood of aneuploid embryos. They specifically looked at how genes play a role in processes like crossover recombination, where chromosomes exchange DNA during egg or sperm formation. They discovered that fewer crossovers are linked to aneuploid embryos, indicating that errors in this process might cause issues with chromosome separation.
The study highlighted specific genes, notably SMC1B and C14orf39, linked to aneuploidy. SMC1B helps maintain chromosome structure, while C14orf39 facilitates chromosome interaction during cell division. This suggests that the same genetic resources affecting crossover recombination also impact the risk of producing aneuploid eggs.
Shai Carmi, a genetics professor not involved in the study, emphasizes its significance in understanding fertility. He notes that while miscarriages are common—affecting 10% to 20% of recognized pregnancies—many conceptions may end before being acknowledged. McCoy estimates that around half of all pregnancies may end very early, often without the couple ever knowing.
This research opens doors for better diagnostics and therapies aimed at reducing pregnancy loss. However, McCoy warns that while genetic variants can provide some insight, they only explain a small fraction of the overall risk for individuals. Despite this, understanding these mechanisms is crucial. McCoy believes that such studies offer fundamental insights into human nature and our reproductive processes.
For more details, you can explore the full study published in Nature.
