Irregular Yolk Sac

Jane Foley's picture


Dear Ms. Ultrasound,
I went for my first ultrasound yesterday and I am about 7 weeks pregnant.

When I asked if everything looked ok the lab tech said yes but it is too early to really say. She showed me the heartbeat and sent the results to the doctor. I went home worry free.

Today I got a call from my doctor saying that I had an irregular yolk sac. She said something about it being thicker than normal. I asked her if I should be worried, and she told me to have another ultrasound.

Is there any more information you can give me about this?



Hello. The yolk sac plays an important part in embryonic development. This part of early pregnancy transfers nutrients to the embryo in the 3rd and 4th weeks. The yolk sac should not grow bigger than 5.6 millimeters in the 5-10 week period of pregnancy. It is a useful predictor of an abnormal pregnancy in an otherwise normal looking ultrasound. So it is possible to see a heartbeat and still have a problem.

In your case, if the yolk sac was "thicker," (not larger) than normal, it has a better prognosis--93% have a normal outcome. If the walls were thicker it is different than a large yolk sac.

If the yolk sac is too big, meaning over 5.6 millimeters, the outcome is not favorable. This means there is an abnormality with the pregnancy and an extremely high risk for miscarriage.

You will now have to clarify what kind of enlargement the yolk sac has, and discuss the possible outcomes, with your doctor.

Hopefully it was an increase in thickness and all will be fine!

With regards,
-- Jane, RDMS