Can Belly Fat Interfere With Ultrasound?

Jane Foley's picture


Dear Ms. Ultrasound,
I am supposed to be 9 weeks pregnant. I recently had an ultrasound in my OB's office which was unexpected and I had just emptied my bladder. He commented that it was difficult to see with the empty bladder but was able to find a sac however could not see anything inside. It looked like there was possibly something (like a shadow) but couldn't be sure and couldn't detect a heartbeat.

In your opinion how likely is it that everything is OK and it was just my empty bladder causing issues. In addition I have a fair amount of abdominal fat which I know made things more difficult to see in my previous pregnancy.


There are two factors that significantly assist a sonographer in producing a diagnostic image of an early gestational sac. The first is having a full bladder.(the bigger the better!) The water in the bladder is a great transmitter of sound waves. This in turn helps us get a good look inside the gestational sac.

The second factor is body habitus. The smaller the body type, the better the resolution of the ultrasound image.

If the sound waves have to travel through a fair amount of fat, then muscle then bowel then hit the uterus and then the gestational sac, and...then have to travel the same path back to the ultrasound probe, a lot of information will be lost because many of the sounds waves have been deflected.

In your case it sounds like the added distance the sound waves had to travel to look at the gestational sac, along with an empty bladder, made it impossible to give any kind of comment on the viability of your pregnancy. I would not worry!! The best exam for your body type is the vaginal probe ultrasound. This puts the ultrasound source right next to the gestational sac, making a fabulous image every time!

With regards,
-- Jane RDMS