Comparison of umbilical artery pulsatility index reference ranges

Area of Science:

• Perinatal Medicine
• Fetal Ultrasound
• Maternal-Fetal Medicine

Background:

• Fetal growth restriction (FGR) poses significant risks to newborns.
• Umbilical artery pulsatility index (UA-PI) is a key ultrasound parameter used to assess FGR.
• Several reference standards exist for UA-PI, but their predictive accuracy is debated.

Purpose of the Study:

• To compare the accuracy of four established UA-PI reference standards.
• To evaluate their effectiveness in predicting small-for-gestational age (SGA).
• To assess their ability to predict adverse neonatal and obstetric outcomes in pregnancies at risk for FGR.

Main Methods:

• Secondary analysis of a prospective ultrasound study (26-36 weeks gestation).
• Included singleton pregnancies with estimated fetal weight or abdominal circumference <20th percentile and available UA-PI.
• Compared predictive accuracy (AUC) of four UA-PI standards (Acharya et al., INTERGROWTH-21st, Fetal Medicine Foundation, Parra-Cordero et al.) for SGA, adverse neonatal, and obstetric complications.

Main Results:

• 207 pregnancies were analyzed; 45.4% had SGA, 24.2% had adverse neonatal outcomes, and 33.3% had obstetric complications.
• All four UA-PI reference standards demonstrated statistically significant but poor predictive accuracy.
• Area under the curve (AUC) values ranged from 0.55 to 0.60 across all outcomes and standards.

Conclusions:

• Existing reference standards for UA-PI have limited predictive value for SGA and adverse outcomes in at-risk pregnancies.
• No single UA-PI reference standard currently outperforms others for these predictions.
• Larger clinical trials are necessary to develop more accurate predictive tools for FGR and associated complications.