The main ideas

So essentially when we watch the fetal heart rate, we are watching to make sure that things are ok with the placenta and the umbilical cord, and thus make sure that baby is getting oxygenated.

The fetal heart rate can help us understand if the baby is getting enough oxygen. And it also gives us clues as to what we can do to help support both mom and baby during the labor. It is important to note that when the fetal heart rate shows accelerations and has normal variability, that the baby is most likely doing fine. However, when it is not normal, it does not always mean that the baby is having major problems. So, you have to take many different factors and assessments into consideration.

References:

Obstetrics: Normal and Problem Pregnancies, 5th ed. Gabbe et al.

Fanaroff and Martin's Neonatal-Perinatal Medicine, 8th ed. Martin et al.