What is the maximum yolk sac size?

• A. 6 mm
• B. 3 mm
• C. 8 mm
• D. 12 mm

Answer: (A)

In early pregnancy ultrasound, yolk sac size helps gauge viability and dating. The yolk sac provides nutrients before the placenta takes over, and its diameter tends to stay within a small range as the pregnancy progresses. A yolk sac diameter up to about 6 mm is considered the upper limit of normal. Values around this size are compatible with a normal early pregnancy, while larger sizes raise concern for potential problems, though they aren’t definitive on their own.

So, the maximum yolk sac size you’d expect in a normal early pregnancy is about 6 mm. A smaller size like 3 mm can be normal too, but it doesn’t represent the upper limit, whereas measurements of 8 mm or 12 mm exceed the normal range and would prompt caution.