Nonstress testing at ≤ 32.0 weeks' gestation: a randomized trial comparing different assessment criteria

Area of Science:

• Perinatal Medicine
• Fetal Monitoring
• Obstetrics

Background:

• Nonstress testing (NST) is crucial for fetal well-being assessment in high-risk pregnancies.
• Established fetal heart rate (FHR) acceleration criteria by the National Institute of Child Health and Human Development (NICHD) are standard.
• Application of these criteria in early gestation (≤ 32 weeks) may prolong NST duration.

Purpose of the Study:

• To compare the time and outcomes of NICHD-defined FHR acceleration criteria (≥ 10 beats/min, ≥ 10 seconds) versus standard criteria (≥ 15 beats/min, ≥ 15 seconds) in preterm pregnancies.
• To evaluate the safety and efficacy of modified NST criteria in early gestation.

Main Methods:

• A randomized controlled trial involving singleton high-risk pregnancies referred for NST at ≤ 32 weeks' gestation.
• Participants were assigned to either the 15 × 15 (standard) or 10 × 10 (modified) FHR acceleration criteria.
• Data collected included NST information, maternal characteristics, and pregnancy outcomes.

Main Results:

• 143 women were randomized (71 to 15 × 15, 72 to 10 × 10).
• The median time to a reactive NST was significantly shorter with the 10 × 10 criteria (37.3 minutes) compared to the 15 × 15 criteria (41.3 minutes; P = .04).
• No serious adverse events were reported in either group.

Conclusions:

• Utilizing the 10 × 10 FHR acceleration criteria reduced the time to achieve a reactive NST by 4 minutes in pregnancies at ≤ 32 weeks' gestation.
• The 10 × 10 criteria appear safe and effective for preterm fetal surveillance, potentially improving efficiency.
• This suggests a viable alternative for optimizing NST protocols in early gestation.