Ultrasound assessment of cricothyroid membrane anatomy before and after labor: a prospective observational study
Main finding · Cricothyroid membrane depthResult — go to the resultMedian difference 0.03 cm 95% CI 0.004–0.09Authors' conclusion
cricothyroid membrane depth increased slightly during labor, but the change fell within expected ultrasound variability and is unlikely to be clinically significant. Neck circumference increased and was associated with body mass index ≥35 and oxytocin dose.
Study context
- Population
- Parturients in early active labor50 analysed
- Exposure
- Post-delivery vs enrollment ultrasound measurements
- Outcome
- Cricothyroid membrane depth (ultrasound)
Methodological detailspaired before–after measurements
- Paired before–after measurements
Main finding
Cricothyroid membrane depth
Median difference
0.03 cm
95% CI 0.004–0.09
P = 0.034
By group
Enrollment
0.80
median · IQR 0.63–0.96 · cm
Post-delivery vs Enrollment
median difference 0.03 cm (95% CI 0.004–0.09); P = 0.034
As reported in the abstract
Observational data: associations, not effects.
Secondary outcomes
| Outcome | Values | Median difference (cm) (95% CI) | P value | |
|---|---|---|---|---|
| Cricothyroid membrane heightPost-delivery vs Enrollment · unchanged | Enrollment median 1.03 (IQR 0.80–1.16) cm | 0.01 (−0.06 to 0.10) | P = 0.85 | |
| Neck circumferencePost-delivery vs Enrollment · significantly greater after labor | Enrollment median 37.0 (IQR 34.5–38.5) cm | 1.0 (0.50–1.50) | P < 0.001 | |
| −1012Difference, cm (linear scale) |
Labor-related factors associated with measurements
- BMI ≥35 and total oxytocin dose associated with increased neck circumference
- No other labor-related factors significantly associated with cricothyroid membrane measurements
Parts of this Brief are withheld: the automatic checks could not confirm them against the abstract.
Original publication
Ultrasound assessment of cricothyroid membrane anatomy before and after labor: a prospective observational study. Int J Obstet Anesth. Published 19 October 2025. doi:10.
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