The Cerebellum (TCD) as EGA Referee

From Dr. Chapa’s OBGYN Clinical Pearls Dr. Chapa’s Clinical Pearls

So, here is a not uncommon situation: A new OB patient presents for initial prenatal care at 28 weeks by “sure LMP” but her ultrasound EGA is just over 3 weeks behind. Simple redating, right? How can we be assured that we are not missing FGR? That is where the “ancillary” use of transcerebellar diameter (TCD) plays a role. In this episode, we will highlight the recent JUNE 2026 data on this and review the 4 scenarios when this supplemental ultrasound finding can play a vital role.

1. Fetal Transcerebellar Diameter Measurement With Particular Emphasis in the Third Trimester: A Reliable Predictor of Gestational Age. AJOG. 2004.

2. Elgadi A, Wagealla M, Idris E, Eissa AYH, Altraifi S, Altraifi H, Abdallah E, Noorallah T, AbdAlla E. Accuracy of Ultrasonographic Transcerebellar Diameter for Gestational Age Estimation: A Systematic Review and Meta-Analysis. J Clin Ultrasound. 2026 Jun 17.

3. ACOG Committee on Obstetric Practice. Committee Opinion No 700: Methods for Estimating the Due Date.Obstetrics and Gynecology. 2017.

4. Arzik IG, Golbasi H, Can ST, Aktas HA, Cakir ZE, Purut CS, Torun R, Toka I, Oztataroglu C, Ekin A. Role of Transcerebellar Diameter in Estimating Gestational Age in the Third Trimester: A Comparative Analysis in Fetuses With Different Growth Patterns. J Ultrasound Med. 2026 Apr;45(4):895-903.