New research showed that monitoring the heart rate of an unborn foal helped veterinarians reliably assess the health of the fetus according to TheHorse.com. The fetomaternal electrocardiogram can consistently detect the cardiac activity of unborn foals starting as early as day 173.

Not only did fetal heart rate monitoring aid veterinarians in observation and diagnosis, but it also showed whether a fetus has died—something difficult to determine with an ultrasound, the most popular technology used to view unborn foals.

The research team at the Graf Lehndorff Institute for Equine Science in Neustadt (Germany) determined that fetal heartbeats at mid-term averaged 110 beats per minute and slowly dropped to around 80 beats per minute by the end of pregnancy. Eighty percent of the fetuses showed a mild increase in heart rate approximately 30 minutes before birth.

Slight rate changes from beat to beat, called heart rate variability, occurred throughout the second half of gestation. In humans, this is a sign of a healthy, normal fetus and is often related to fetal activity. Though fetal heart rate tended to increase during foaling, HRV did not decrease, as it does during birth in most species. As HRV is frequently associated with stress levels, this could suggest that the birthing process is relatively stress free for foals.