A short cervix only guides treatment if the measurement is reliable. Transvaginal ultrasound is the standard; transabdominal views are affected by bladder filling and often overestimate length. Ask the woman to empty her bladder, place the probe in the anterior fornix without pressing, obtain a sagittal view showing the whole canal from internal to external os, and measure in a straight line. Take three measurements over a few minutes and record the shortest good-quality one, watching for funnelling or dynamic change with gentle fundal pressure.
- Use transvaginal, not transabdominal, ultrasound to measure cervical length
- Scan with an empty bladder and avoid pressing on the cervix with the probe
- Record the shortest of three good-quality measurements
- Note funnelling and any change during the scan
Why it matters
Treatment thresholds are only meaningful when the measurement behind them is technically sound.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for obstetrics & gynaecology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free