Two Sacs...One Baby and Heartbeat

QUESTION

Dear Ms. Ultrasound,
Hi. I am 7 weeks 3 days and I had my first ultrasound last week. In the ultrasound, they saw what appeared to be two sacs. One had a visible baby with a good strong heartbeat, but one looked empty or at least we didn't see anything. The doctor came in and looked at the ultrasound and stated that it may only be one sac and there could be a thyroid pushing up in the middle of it to make it look like two.

What are the chances this could be a second baby? Can one twin be growing at a slower speed? Could I have had implantation in the second egg a day or two after the first? Crazy I know but I am so confused. I go back in 2 weeks to see what is going on.

ANSWER

Hello
If the doctor saw two sacs at 7 weeks, there should be a fetal pole in each sac if the pregnancy is growing at a normal rate.

I think what the doctor was saying was there may be what is called a fibroid (not a thyroid) pressing into the gestational sac to make it look like two sacs. (The thyroid is an organ in your neck).

A fibroid is a common benign tumor that can grow in the uterus as a woman ages. Fibroids don't normally present themselves until a woman get into her mid to late thirties.
As far as implantation is concerned,even if two eggs implanted on different days as you suggested, two fetal poles with heartbeats would have been obvious at the time of you ultrasound.

So I really don't It sound like there is a chance you will be having twins, as only one fetal pole was seen on your first ultrasound.

With Regards,
--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.