Defining safe criteria to diagnose miscarriage: prospective observational multicentre study

Area of Science:

• Early pregnancy assessment
• Clinical ultrasonography
• Reproductive medicine

Background:

• Diagnosing miscarriage relies on specific ultrasound measurements like crown-rump length (CRL) and mean gestational sac diameter (MSD).
• Recent changes in guidance have updated these cut-off values.
• The performance of these new criteria and optimal follow-up protocols require validation.

Purpose of the Study:

• To validate updated cut-off values for CRL and MSD in diagnosing miscarriage.
• To assess the influence of gestational age on these measurements.
• To determine optimal scan intervals and findings for definitive pregnancy failure diagnosis.

Main Methods:

• A prospective, multicentre observational trial involving 2845 women with pregnancies of unknown viability.
• Transvaginal ultrasonography was used to measure MSD and CRL, and assess embryo heart activity.
• Follow-up scans were performed 7-14 days later, with final viability assessed at 11-14 weeks' gestation.

Main Results:

• Updated cut-off values (MSD ≥ 25 mm, CRL ≥ 7 mm) showed 100% specificity for miscarriage diagnosis at initial scans.
• Specific criteria for empty sacs and absent embryo heart activity also demonstrated 100% specificity.
• Repeat scan findings, such as persistent absence of embryo heart activity or lack of MSD growth, were highly specific for miscarriage.

Conclusions:

• The recently revised cut-off values for diagnosing miscarriage using ultrasound are appropriate but do not fully incorporate gestational age.
• Current recommendations for the timing and expected findings of follow-up scans appear too liberal.
• Protocols for miscarriage diagnosis need revision to incorporate these findings, preventing misdiagnosis and unnecessary termination of viable pregnancies.