Progestagen profiles during the last trimester of gestation in Thoroughbred mares with normal or compromised pregnancies.

The study investigates the presence of progestagens (namely, progesterone and pregnenolone) in the bloodstream of pregnant thoroughbred mares. It aims to discover their possible correlation with the health of the pregnancy, by comparing horses with healthy and compromised pregnancies.

Study Objective and Methodology

• The primary objective of this research was to identify specific progestagens present in pregnant mares’ blood plasma and find out if the concentration of these progestagens differ between those with healthy and compromised pregnancies.
• Detailed studies were performed on a group of 19 healthy mares and 14 mares with potential complications such as placentitis, uterine torsion/rupture, colic, and laminitis.
• Blood samples were collected between 243 and 351 days of gestation and subjected to gas chromatography-mass spectrometry to identify ten progestagens.

Findings

• Seven out of ten progestagens showed a significant surge with increasing gestational age in healthy mares, while progesterone was undetectable.
• Concentrations of pregnenolone and/or progesterone as well as various metabolites increased in mares with placentitis. This suggests that fetal production of these hormones enhanced; moreover, metabolism in the utero-placental tissues also increased due to chronic stress.
• Mares with other types of placental pathology showcased elevated progesterone concentrations. On the other hand, the concentrations of 5alpha-DHP and 3beta-5P were low, which could indicate a reduction in placental function.
• If the mares experienced complications unrelated to the placenta, most progestagens were significantly lower than those of the control group.

Conclusions

• Progestagen profiles varied visibly between normal and abnormal pregnancies.
• However, no conclusive evidence was found to confirm any link between maternal plasma concentrations of either progesterone or 5alpha-DHP or any other progestagen, and the maintenance of pregnancy.

This indicates that the function or role of these hormones in maintaining pregnancy in mares may be more complex than initially thought, lending the need for further in-depth research.