Transperineal ultrasound can be used to measure fetal station during labor

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Takeaway

  • 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.

Key results

  • 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.

Study design

  • 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.

Limitations

  • Homogeneous population; mainly Chinese women.