- Ultrasound measurements can provide objective measures of labor progress.
- Parity, obesity, and method of induction appear to affect the rate of head descent in labor.
Why this matters
- Labor curves in modern pregnant populations may differ from those established by Friedman.
- Vaginal exams are subjective; intrapartum transperineal ultrasound has emerged as a noninvasive tool to objectively assess labor progress.
- Angle of progression (AOP) and head-perineum distance (HPD) can be used to assess labor progress, but management should be adjusted to patient characteristics.
- Parity and method of induction affected head descent; multiparity and induction of labor with artificial rupture of the membranes or intracervical balloon had steeper HPD slopes.
- Epidural was associated with a slower rate of fetal head descent determined by both HPD and AOP.
- Obesity was associated with a higher overall HPD and decreased HPD for each unit increase in cervical dilatation compared with normal-weight women.
- Prospective longitudinal study.
- Singleton pregnancies undergoing induction of labor at term at a single hospital between 2016 and 2017 (n=315).
- Transperineal ultrasound for AOP and HPD performed along with serial vaginal exams.
- Funding: None disclosed.
- Homogeneous population; mainly Chinese women.