False reactive nonstress tests in postterm pregnancies

Area of Science:

• Obstetrics and Gynecology
• Fetal Monitoring
• Perinatal Medicine

Background:

• Postterm pregnancies pose increased risks to fetal well-being.
• Nonstress tests (NSTs) are commonly used to assess fetal health in high-risk pregnancies.
• Evaluating the accuracy of NSTs in postterm patients is crucial for timely intervention.

Purpose of the Study:

• To evaluate the efficacy of the nonstress test (NST) in identifying fetal distress in postterm pregnancies.
• To determine the false reactive rate of the NST in this patient population.
• To compare the utility of the NST with the oxytocin challenge test (OCT) for assessing fetal well-being in postterm infants.

Main Methods:

• A retrospective study of 125 postterm patients with reactive NSTs.
• Analysis of pregnancy outcomes, including antepartum deaths, neonatal deaths, infant brain damage, and fetal distress.
• Comparison of NST results with outcomes and evaluation of the OCT's performance.

Main Results:

• A false reactive rate of 8% was observed for the NST, indicating a significant rate of false reassurance.
• Ten poor outcomes occurred, including four antepartum deaths, one neonatal death, one brain-damaged infant, and four cases of fetal distress.
• Cord compression was identified as a major cause of acute fetal distress, often associated with uteroplacental insufficiency.

Conclusions:

• The nonstress test (NST) can be misleading in postterm pregnancies, providing false reassurance of fetal well-being.
• The oxytocin challenge test (OCT) demonstrated utility in identifying fetal distress related to cord compression.
• The OCT may serve as a more sensitive indicator of fetal well-being and distress in the postterm population compared to the NST.