Early deceleration – Head compression
The shape of early decels resembles that of late decels. It is a gradual decrease in the FHR with onset to nadir ≥ 30 seconds. The deceleration begins with a contraction and the nadir occurs at the same time as the peak of the contraction.
What to do? Nothing. Allow the labor to continue. It is not clinically significant.
Variable decelerations – Chord compression
Shape: Like a V or U. It is a sharp, abrupt drop in heart rate and quick rise back. Variable decels can occur anywhere.
Late decelerations – Uteroplacental insufficiency
(e.g. if you have a bunch of contractions happening back to back (tachysystole), then you don’t have enough time for uterine perfusion, and then you can start having late decels. If there is maternal HoTN like from an epidural and not enough uterine perfusion pressure, then you can have late decels. If mum becomes hypoxic for any reason or decreased oxygen carrying capacity, then you have late decel.
If late decels are accompanied by a flat trace and no beat to beat variability, it is worrisome and correlates with fetal acidosis.
Sinusoidal Pattern – Severe fetal anemia or acidosis
Also occurs with certain narcotics. e.g. butorphanol or nalbuphine.