Prediction of labor outcome by measuring the angle of progression using two dimensional trans-perineal Ultrasound: A prospective cohort study

Abstract

Background: Failure of descent due to fetal malposition is one of the most common indications for performing surgical deliveries. It has recently been suggested that trans-perineal intra-partum ultrasonography may be useful in assessing fetal head engagement, position and station as well as it’s reliable, cheap, painless and effective tool. Measuring the ‘angle of progression’ could assist in the obstetrician’s decision regarding mode of delivery. Objectives: The primary outcome is to use the AOP to develop a predictive model for the probability of successful vaginal delivery. Secondary outcomes including assessment of possibly successful VBAC in previous one CS women. Methods: We recruited 500 women in labor. For each woman, a (TPU) was performed to measure the AOP in late first and second stages of labor. We compared AOP between women who delivered fetuses through vaginal route to those who delivered by CS. Results: Through 467 women included in the study, AOP was significantly Higher in spontaneous vaginal delivery group (with cut off 123°±8.5°) as compared with women delivered by vacuum or by CS (113°±10.5°) (P=0.003). The VBAC as another secodary outcome seems to be insignificant. Conclusions: TPU is safe, non-invasive and easily preformed technique which is useful to predict labor outcomes.

Utility of Ultrasonographic Parameters for Monitoring of Progress of Labor and Prediction of Successful Vaginal Delivery: Narrative Review

“…Angle of progression was significantly higher in spontaneous vaginal delivery group (with cutoff 123° ± 8.5°) as compared with women delivered by vacuum or by CS (113° ± 10.5°) (p = 0.003). 30 In India, a study conducted in 2021 on 200 subjects where AOP was determined by transperineal USG concluded that the probability of CS was nil at an angle ≥116° during the first stage of labor. The cutoff value of AOP for predicting vaginal delivery was 99.6° as determined by ROC.…”