Will It Be Obviously Twins?


Dear Ms Ultrasound,
I had an u/s today at just over 5 weeks. The nurse called the doctor in to look at the screen because there were two gestational sacs. They said that I need to return in two weeks for another u/s because they could not determine much at this point or whether both sacs will continue to term.One sac was smaller than the other -- about half the size and flatter in appearance. The doctor said that the larger sac measured to be 5 weeks. Can you shed any light on this finding? What are the statistics regarding having two gestational sacs? How common is it? When I go back in 2 weeks will it be obvious if I am having twins?



Hi Elisa,
You had an ultrasound too early to make any kind of diagnosis. 2 sacs are not uncommon to see on an early ultrasound. Since we have had the technology to appreciate early pregnancies, we discovered that twins happen much more than anyone really knew.

What than happens is, upon a second look, many times one of the gestational sacs has not grown. This is not to say this is the case with you. Just a bit of information on this subject matter of early twin detection.

I cannot really comment any more than to say that you must wait a couple of weeks and have a second ultrasound to learn anything about your pregnancy. You will know for sure at the next ultrasound if you have 2 fetal poles (babies) and 2 heartbeats. If you have 2 heartbeats things will be looking good for twins.

-- Jane, RDMS

Jane Foley

Jane Foley has worked as a Sonographer (Ultrasound Technologist) since 1979. Jane has lived and worked in many parts of the world including Saudi Arabia. She is a Registered Diagnostic Medical Sonographer or RDMS. She pulls a wealth of information from her experience in the field of Radiology and her interactions with such a broad cross-section of cultures she has visited. She now makes her home on the island of Maui with her English husband, Michael.