A study on horses helps to better understand the origin of miscarriages that occur during the first two months of pregnancy.
- Horses share many similarities with humans in terms of chromosomes and pregnancies, making them a good research model for studies of miscarriage.
- One study estimates that 42% of miscarriages during the first two months of pregnancy are due to complications linked to the presence of a third complete set of chromosomes in the fetus, an anomaly called triploidy.
- Mares have a similar gestation period: 11 months compared to nine months for women. Embryos develop at a similar rate in the early stages.
10% to 20% of human pregnancies end in miscarriage during the first trimester. While they are generally associated with chromosomal errors, the mechanisms and causes remain quite mysterious. But horses could help to better understand these spontaneous pregnancy terminations, according to a study from Cornell University published in the journal Proceedings of the National Academy of SciencesAugust 5, 2024.
Early miscarriages: are chromosomal abnormalities the cause?
Studying 256 fetal and placental samples from veterinarians who had treated mares with failed pregnancies, the researchers found that chromosomal errors were present in more than 5 out of 10 miscarriages that occurred before day 110 of gestation. They were present in only 1.4 percent of cases beyond three and a half months.
“Aneuploidy (loss or gain of a single entire chromosome) was mainly associated with miscarriages in the first 10 weeks of pregnancy, while deletions or duplications of only part of a chromosome were observed in miscarriages after 110 days,” specifies the press releaseThe team also found that 42% of miscarriages in the first two months of pregnancy were linked to the presence of a third complete set of chromosomes in the fetus, an abnormality called triploidy.
Why is this discovery interesting for human health? “During this embryonic period [jusqu’à huit semaines après la conception]triploidy has rarely been reported in mammals other than females”explains lead author Mandi de Mestre. “The study tells us that in the first six weeks of gestation, this is likely to be the leading cause of miscarriage after natural conception.”
How horses help us better understand miscarriages
In their press release, the scientists point out that research into the causes of miscarriages in women in early pregnancy is difficult because the fetuses are “usually lost at home, leaving scientists without equipment – or data – to study.”
Furthermore, work with animals such as mice has many limitations because of their differences from human pregnancies. On the other hand, horses prove to be a good model. Indeed, mares have a similar gestation period – 11 months compared to nine months in women – and the embryo develops at a similar rate in the early stages. In addition, the genetic content in the chromosomes is very similar between the two species. “Which makes them particularly relevant for the study of chromosomal errors”the team adds.
So for scientists, beyond providing a better understanding of the genetic causes of spontaneous terminations of equine pregnancies, this research gives “an overview of the frequency of chromosomal errors over the equivalent period of the first six weeks of human gestation” and identifies “horses as an excellent model for studying human miscarriages.”
