Using a fetomaternal electrocardiogram (ECG, a noninvasive way to measure electrical changes in the heart) to monitor the fetal heart rate in the last two months of a high-risk pregnancy can help determine whether the unborn foal is healthy, according to Christina Nagel, MSc, PhD, at the Graf Lehndorff Institute for Equine Science in Neustadt, Germany. Using that technology, Nagel et al. recently completed a study in which they examined heart rate and heart rate variability in the pregnant mare and her fetus.

"In contrast to other methods (of monitoring the pregnancy, such as transrectal palpation or transabdominal ultrasonography), which show only a short period, the fetal ECG can be used for long-term monitoring so that it is possible to get a good evaluation of the fetal well-being," Nagel explained.

Fetomaternal ECGs were first evaluated in 2010 as a fetal monitoring tool. In the current study Nagel et al. aimed to determine the normal values in heart rate (HR) and heart rate variability (HRV, the slight changes in heart rate from beat to beat) of the pregnant mare and her fetus, and to detect physiological changes during ongoing gestation.

Nagel and her team monitored seven Warmblood broodmares (aged 5 to 20 years) and their fetuses during the last two months of pregnancy and parturition (labor) with ECG equipment to gain a better understanding of how the two cardiovascular systems function together.

Key findings in the study included:

  • Overall, there was no significant increase in the mares’ heart rates throughout gesta