Sonography Assessment of Gestational Age

Excerpt

Recent studies continue to support 1st-trimester ultrasonography as the most reliable method for determining gestational age while also refining measurement interpretation. New crown-rump length (CRL) dating formulas derived from pregnancies with known conception dates demonstrate improved precision compared with older reference equations, with most estimates falling within 0 to 2 days of the true gestational age (see Image. Crown-Rump Length Measurement). Recently published early pregnancy reference charts based on accurately dated pregnancies, including assisted reproductive technology cohorts, suggest that traditional curves based on the last menstrual period (LMP) may slightly overestimate gestational age at the extremes of early development, supporting the use of updated population-specific charts.

Beyond improvements in biometric standards, advances in ultrasound technology have expanded the role of point-of-care imaging. Studies evaluating artificial intelligence–assisted and portable ultrasound devices show gestational age estimates obtained by novice users are comparable to those generated by experienced sonographers using high-end machines, particularly in the 2nd trimester. Deep learning-based approaches further demonstrate the ability to estimate gestational age with mean errors of only a few days across multiple trimesters, sometimes outperforming conventional biometric methods.

Measurement of CRL on the 1st-trimester ultrasound between 8 weeks 0 days and 13 weeks 6 days is the most accurate approach to gestational age dating and is the gold standard for pregnancy assessment. Recent findings suggest that updated reference data and emerging artificial intelligence-supported technologies may further improve accuracy, consistency, and access to reliable gestational age evaluation across diverse clinical settings.