Prediction of labor outcome using serial transperineal ultrasound in the first stage of labor.

Objective: The objective of this study is to evaluate the feasibility of predicting labor outcome using serial transperineal ultrasound (TPU) in the early active phase of labor.

Methods: This is a single center prospective observational study in a tertiary obstetrics unit in Hong Kong. Nulliparous women carrying singleton pregnancy at the onset of active phase of labor were recruited. Serial 3D volumes by TPU were acquired and then repeated after 1 and 2 h, which were subsequently analyzed for fetal head symphyseal distance (HSD), angle of progression (AoP), and fetal head progression distance (PD). The women were classified into two groups, according to whether they had vaginal delivery or cesarean section (CS) for reasons other than non-progressive labor (Group A) or CS for non-progressive labor (Group B). The TPU parameters were then compared between the groups.

Results: Group A consisted of 74 (60.0%) women with vaginal delivery, 27 (21.8%) with instrumental delivery and 3 (2.4%) CS for reasons other than non-progressive labor, while Group B consisted of 20 (16.1%) women who had a CS for non-progressive labor. Group B had a significant slower hourly progression rate of AoP, HSD, and PD at 1-h and 2-h from the initial assessment, compared with Group A. Multivariate logistic regression analysis demonstrated that PD progression at 2-h and the use of oxytocin were significant independent predictors for CS for non-progressive labor.

Conclusion: It is feasible to predict CS for non-progressive labor in the early active phase of labor by a slower rate of fetal head descent determined by TPU.