How Likely is a Vanishing Twin?

QUESTION

Dear Ms Ultrasound,
I am 27 years old and pregnant for the 6th time. I have two children, 8 years and 3 years and have suffered 3 early miscarriages. My last period was May 13, 2004.

I had an ultrasound about 2 weeks ago which showed two gestational sacs -- one a little smaller than that other. Today, I had a follow up and found two babies, both with good heartbeats. Twin "A" was 156 and Twin "B" was 162. Both measure about 7 weeks and a few days. Twin "A"'s sac is considerably smaller than Twin "B"'s though and the doctor said that this could result in a vanishing twin; however, with the good heartbeat and measurements, the pregnancy may progress normally.

What is the chance of a vanishing twin after a strong heartbeat and good measurements? And what effects does a vanishing twin have on the surviving twin?

Thanks.
Kim

ANSWER

Hi Kim,
Congratulation on your twins! Two heartbeats up in the hundred fifty plus range is a good first sign! From my experience, a baby that is about to get into trouble heart rate drops below hundred. That's when I begin to worry.

I don't know what considerably smaller means when the Doctor was describing the smaller sac. If they both measured 7 plus weeks they must be fairly close in size. I do not know the percentage of twins that do not make it. It sure sounds to me like you are on a good track with these two.

If a twin does not make it, especially this early there is no effect on the other twin.What I do like to share is how important I think it is that a mother stop the medical chatter in her brain, that results in a lot of anxiety. Let it all go. Enjoy every moment with these blessings you created, starting now.

-- 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.