What is defined as an unsatisfactory CST?

An unsatisfactory contraction stress test (CST) is defined by the criterion of fewer than three contractions occurring within a 10-minute period. This standard is essential because the CST aims to assess the fetal heart rate response to contractions, simulating the stress of labor. A test with insufficient contractions would not provide adequate data to evaluate the fetus's well-being and its tolerance to labor conditions, leading to the classification of the test as unsatisfactory.

In assessing the other options, the presence of late decelerations is indicative of potential fetal distress and would not categorize the test itself as unsatisfactory but rather provide vital information about fetal status. A normal fetal heart rate baseline is a reassuring finding; however, it does not pertain to the sufficiency of the test itself in terms of contractions. Increased uterine activity can reflect uterine overactivity but does not define the CST's adequacy in terms of the number of contractions required for evaluation. Therefore, the criterion of fewer than three contractions is the key determinant of an unsatisfactory CST.