By Haley Masterson
Reading your first fetal heart tracing can be intimidating, but you will be a pro at interpreting accelerations, early decelerations, variable decelerations, and late decelerations once you read a few hundred of them. Until then, keep this mnemonic close at hand…
The trick to this mnemonic is writing it so each letter is associated with the one beneath it, like so:
- Variable decelerations are associated with cord compression. (V and C)
- Early decelerations are associated with head compression. This is generally a benign event. (E and H)
- Accelerations are associated with oxygenation – which explains why they’re generally a good prognostic factor. (A and O)
- Late accelerations are associated with placental insufficiency. (L and P)
Variable decelerations are the most common of the decelerations but also the most complex. The exact shape of the deceleration is determined by whether the uterine artery or vein is occluded first – but the important thing to remember is that it’s caused by compression of the umbilical cord. Unlike early and late decelerations, variable decelerations are not gradual. This works to your advantage, as their relative abruptness makes them easy to pick out in a monitoring strip.
The “early” in “early deceleration” refers to the lowest point of the deceleration occurring at the same time as the peak of the contraction. They are a result of increased vagal tone secondary to head compression and are generally benign when they occur during the 1st or 2nd stage of labor – but they can be a sign of cephalopelvic disproportion if they persist.
The “Late” in “Late decelerations” refers to the lowest point of the deceleration occurring after the peak of the contraction. Maternal contractions constrict the placental blood supply, thereby limiting the fetus’ blood supply to what’s already stored in the placental reserve. In the case of uteroplacental insufficiency, this lack of oxygen results in a deceleration which occurs as a result of (i.e. after) the contraction.
• Fauci, Anthony S. Harrison’s Principles of Internal Medicine / Editors, Anthony S. Fauci … [et Al.]. 17th ed. New York: McGraw-Hill Medical, 2008.
• Misra, Renu, and Ian S. Grundsell. Electronic Fetal Heart Monitoring. B.I. Publications, 2001.