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Expected-value bias in mid-trimester preterm birth screening.

A Aiartzaguena1, A Del Campo1, I Melchor1

  • 1Hospital Universitario Cruces, Biocruces Bizkaia Health Research Institute, UPV/EHU, Bizkaia, Spain.

Ultrasound in Obstetrics & Gynecology : the Official Journal of the International Society of Ultrasound in Obstetrics and Gynecology
|September 20, 2021
PubMed
Summary
This summary is machine-generated.

Masking cervical length (CL) measurements during mid-trimester ultrasounds significantly increased the detection of short cervix, a preterm birth risk factor. This blinding strategy improves screening accuracy for preterm birth prevention.

Keywords:
blindingcervical lengthexpectancy biasexpected-value biasobserver biasobstetric ultrasoundpreterm birth screeningshort cervix

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Area of Science:

  • Obstetrics and Gynecology
  • Maternal-Fetal Medicine
  • Diagnostic Imaging

Background:

  • Short cervical length (CL) ≤ 25 mm in mid-trimester ultrasound is a risk factor for preterm birth.
  • Vaginal progesterone is a recommended treatment for short cervix to prevent preterm birth.

Purpose of the Study:

  • To evaluate observer bias in cervical length (CL) measurements.
  • To assess the impact of masking CL measurements on short cervix prevalence during routine mid-trimester ultrasound scans.

Main Methods:

  • A 2-month flash study at Cruces University Hospital masking CL measurements during routine mid-trimester scans.
  • Comparison of short cervix prevalence between a blinded group (n=457) and a non-blinded control group (n=526).
  • Standardized treatment with vaginal progesterone for short cervix was maintained in both groups.

Main Results:

  • The prevalence of short cervix was significantly higher in the blinded group (5.5%) compared to the non-blinded group (2.7%) (P=0.024).
  • A statistically significant difference was observed in the incidence of CL measurements between 24-25 mm, with lower prevalence in the non-blinded group (0.6% vs 2.4%; P<0.005).
  • CL values showed a normal distribution in the blinded group, contrasting with a skewed distribution in the non-blinded group.

Conclusions:

  • Expected-value bias in CL measurement for preterm birth screening is confirmed.
  • Blinding CL measurements is an effective strategy to enhance the performance of cervical length screening in clinical practice.