A study of horses, which have similar chromosomes and pregnancies to humans, found that 42% of miscarriages in the first two months were due to triploidy, an extra set of chromosomes.
Mandi de Mestre from the College of Veterinary Medicine from Cornell University noted that triploidy is rarely seen in mammals other than humans during the first eight weeks. This study suggests that in the first six weeks of pregnancy, triploidy is likely the main cause of natural pregnancy loss.
De Mestre is the main author of a study titled “Naturally Occurring Horse Model of Miscarriage Reveals Temporal Relationship Between Chromosomal Aberration Type and Point of Lethality,” published in the Proceedings of the National Academy of Sciences on August 5.
Human miscarriages occur in 10-20% of pregnancies and are often linked to chromosomal errors, but no animal models have perfectly replicated this condition. The new study shows that horses can help veterinarians understand pregnancy loss and serve as a model for human miscarriage.
De Mestre said, “We studied chromosome errors throughout horse pregnancies and found that triploidy is linked only to early pregnancy losses.”
In the study, de Mestre’s lab at Cornell and previously at The Royal Veterinary College, London, received 256 fetus and placenta samples from horses with failed pregnancies over ten years. Researchers investigated chromosomal errors in these samples and found that these errors caused 57.9% of pregnancy losses up to day 55, 57.2% of losses between days 56 and 110, and only 1.4% of losses after day 111.
Aneuploidy was linked to early miscarriages, while partial chromosome deletions or duplications were linked to later miscarriages. These findings are similar to those seen in human studies.
Horses are a good model for studying human pregnancies due to their similar gestation period (11 months vs. nine months in humans) and the similar rate of early embryo development. Additionally, horse chromosomes are genetically similar to human chromosomes, making them relevant for studying chromosomal errors.
Determining the reasons for early miscarriage in women is difficult because most losses happen at home, leaving little material for study. This study provides insight into chromosome errors in early pregnancy, using horses as a model due to their high level of care and routine tracking. Unlike mice, horses have a gestation period similar to humans and offer better data for research.
The study reveals common chromosomal abnormalities in horses, which will change how veterinarians manage pregnancies. For example, if a major chromosomal error is detected, clinicians might avoid extending the pregnancy with hormones.
The findings will also lead to new diagnostic tests for chromosome abnormalities in horse fetuses.
“This research helps understand the genetic causes of pregnancy loss in horses,” said Shebl Salem, a postdoctoral researcher and co-first author of the study.
Horse miscarriages provide valuable insights into early human pregnancy loss. Studying horses helps researchers understand how chromosomal errors cause miscarriages, offering a better model than mice due to their similar gestation period and care levels.
This research can improve the management of horse pregnancies and may lead to better diagnostic tests and treatments for both horses and humans.
Journal reference :
- Jessica M. Lawson, Shebl E. Salem et al., Naturally occurring horse model of miscarriage reveals temporal relationship between chromosomal aberration type and point of lethality. PNAS. DOI: 10.1073/pnas.2405636121.