What is the maximum gestational sac size reported at 10 weeks gestation?

• A. 10 mm
• B. 5 mm
• C. 20 mm
• D. 15 mm

Answer: (B)

In early pregnancy, the gestational sac size (mean sac diameter) is one of the first ultrasound measurements used to estimate gestational age and assess viability. The sac grows quickly early on, and the reference values set the benchmark for what’s considered a normal sac size at specific early weeks.

At around 10 weeks, the size that’s often cited in standard references for the gestational sac is about 5 mm. The larger numbers (10, 15, 20 mm) don’t fit the typical sac size associated with this stage in common reference charts, and by 10 weeks the emphasis shifts more toward crown-rump length for dating rather than the sac diameter. So 5 mm is the best-match value for this context.