Contraction stress test

Overview
A contraction stress test (CST) is performed near the end of pregnancy to determine how well the fetus will cope with the contractions of childbirth. The aim is to induce the contractions and monitor the baby to check for heart rate abnormalities. It involves the release of oxytocin into the blood stream of the pregnant woman by the stimulation of the nipples. The target is to achieve around three contractions every ten minutes.

An oxytocin challenge test (OCT) is sometimes performed afterwards, usually if the CST failed to give clear readings or the uterus did not contract at an appropriate rate. This involves oxytocin being given to woman via an intravenous drip.

The test returns positive if there are noticeable decelerations of the heart rate during over half of the contractions.

History
The test was first introduced in 1972 and was standardised in 1975 when the parameters of contraction number and frequency were given.

Contraindications
This "stress test" is usually not performed if there are any signs of premature birth or placenta praevia.