# Hair Allopregnanolone in Mares and Foals as a Retrospective Biomarker of Predicting Feto-Maternal Well-Being

## TL;DR

This study shows that allopregnanolone levels in horse hair can predict the health of foals and their mothers during pregnancy.

## Contribution

The study introduces hair allopregnanolone as a novel retrospective biomarker for feto-maternal well-being in horses.

## Key findings

- Lower foal ALLO and foal/mare ALLO ratio were observed in sick foals compared to healthy ones.
- ALLO concentrations strongly predicted foals’ clinical outcomes with 86.8% accuracy.
- Positive correlations were found between ALLO levels and gestation length, foal weight, and Apgar score.

## Abstract

Successful pregnancies require several adaptations in the mare, and steroid hormones induce, organize, and maintain many of these adaptations. Allopregnanolone (ALLO), a neurosteroid and progesterone metabolite, is of particular interest. During pregnancy, ALLO is produced in increasing amounts by the mare, the placenta, and the fetal brain, gonads, and adrenal glands. Since a single hair sample taken at birth offers insights into a prolonged yet identifiable prenatal period, the authors examined the possible role of ALLO as a biomarker predicting feto-maternal well-being by the hair of both mares with normal or high-risk pregnancies and their respective healthy and sick foals. Since the prenatal activity of the hypothalamus–pituitary–adrenal axis is crucial for the ultimate maturation of the fetus and its adaptation to extra-uterine life, the lower ALLO concentrations in sick foals observed in the present study deserves further attention as a potential new biomarker of prenatal disease.

Assay of steroid hormones in hair has become an attractive alternative for studies focusing on the perinatal period in equine medicine. The aim of the present study was to evaluate mares’ and foals’ hair ALLO concentrations and their ratio in relation to clinical conditions and selected clinical parameters. The 37 mare–foal pairs were categorized into healthy (group H; n = 15) and sick (group S; n = 22) groups. ALLO from hair was measured using a commercial ELISA kit. Foal ALLO and foal/mare ALLO ratio were lower in group S compared to group H (p < 0.001). Moderate positive correlations were found between both the foal ALLO and foal/mare ALLO ratio and the mare’s gestation length (p = 0.003; r = 0.476 and p = 0.002; r = 0.487), between the foal ALLO and foal’s weight (p = 0.042; r = 0.336), and between the foal/mare ALLO ratio and foal’s Apgar score (p = 0.047; r = 0.410). Based on a logistic regression model, a strong relationship (R2 = 0.75) emerged between ALLO concentrations and foals’ clinical outcome, with concentrations of the hormone predicting foals’ clinical outcome with high accuracy (86.8%). Decreased foal ALLO and foal/mare ALLO ratio in sick foals appear to be potential biomarkers of prenatal disease toward the end of pregnancy.