Duration of continuous fetal gastrointestinal peristalsis before parturition in mares maintained at a breeding farm or in a university hospital.

Overview

• This study investigated whether continuous fetal gastrointestinal peristalsis detected by ultrasound (termed Phase 5) is a reliable indicator of fetal maturity in pregnant mares and whether environmental stress from hospitalization affects the duration of Phase 5 or gestation length.

Background and Purpose

• Mares show variability in gestation length, making it hard to predict exact fetal maturity based on duration alone.
• Currently, no standard clinical method exists to accurately assess fetal maturity in horses before birth.
• In human and canine fetuses, continuous gastrointestinal peristalsis before delivery indicates fetal readiness to survive after cesarean section.
• The study aimed to evaluate if continuous fetal gastrointestinal peristalsis (Phase 5) can similarly serve as a maturity marker in horse fetuses.
• Researchers also tested if mares in a potentially stressful environment (hospitalized) differ in gestation duration or Phase 5 length compared to mares at their home breeding farm.

Hypotheses

• Hospitalized mares, due to stress, would have longer gestation periods than mares at breeding farms.
• Hospitalized mares would experience a longer duration of Phase 5 fetal gastrointestinal peristalsis compared to farm mares.

Methods

• Late-gestation mares were divided into two groups: mares managed extensively at a breeding farm and mares hospitalized in a university veterinary teaching hospital.
• Fetal gastrointestinal tract motility was monitored ultrasonographically to identify the onset and duration of continuous peristalsis (Phase 5).
• Gestation length and Phase 5 duration were measured and adjusted for potential confounders like foal sex.

Results

• Gestation length, after statistical adjustment, was not significantly different between hospital and farm mares:
  • Breeding farm group: 353.6 days (95% CI: 351.0-356.1)
  • Hospital group: 345.5 days (95% CI: 336.8-354.2)
• Phase 5 continuous fetal gastrointestinal peristalsis was observed in all mares shortly before parturition.
• The duration of Phase 5 was significantly longer in hospitalized mares compared to breeding farm mares:
  • Hospitalized mares: 17.6 days (95% CI: 13.1-22.0)
  • Breeding farm mares: 10.7 days (95% CI: 9.0-12.5)

Conclusions

• Continuous fetal gastrointestinal peristalsis (Phase 5) can reliably indicate impending parturition and potentially fetal maturity in mares.
• The hypothesis that hospitalized mares would have longer gestation was not supported; however, the longer duration of Phase 5 in hospitalized mares suggests stress or environmental factors may impact the timing of gastrointestinal maturation or fetal readiness.
• This marker could aid veterinarians in managing high-risk pregnancies and timing interventions such as induction or cesarean section more accurately.
• Additional research is necessary to determine precisely when Phase 5 onset corresponds with sufficient fetal maturity for safe delivery or intervention.