Twins are Different Sizes


Dear Midwife,
I found out via ultrasound on October 28th that I am pregnant with identical twins (in the same sack). On 10/28, the larger twin (twin A) was measuring 5 weeks 6 days with a faint heartbeat. Twin B was smaller (I don't know how much smaller), and no heartbeat was detectable. 5 days later, on November 2, I had a follow-up ultrasound b/c of bleeding. Twin A is now measuring 7 weeks 4 days, and twin B is measuring between 5 weeks 6 days and 6 weeks 1 day. No heartbeat for twin B yet.

Is it common to get a heartbeat for 1 twin but not the other? If Twin B is 5 weeks 6 days, is it possible that the heartbeat simply was detectable? Or do I need to give up on my hopes of having twins?



It is really too soon to say one way or the other. This is one of those times when patience is all we have to offer, sorry. Worrying certainly will not help the situation. So love both your children as much as you can; we really have very little time with any of our children, and I think we should enjoy them whenever we are blessed to be able to.

-- Cynthia, CNM. PhD.


I had a similar situation

I had a similar situation with my first pregnancy. It turned out my son had an acardiac twin (TRAP sequence). You should definitely keep following up with your doctors. twin to twin transfusion syndrome is another condition that can result in twins of different sizes. I don't want you to panic-only your doctors can diagnose any condition, but TRAP is rare and it was hard for me to connect with any one else who had experienced it. Take care of yourself!

Cynthia Flynn

Cynthia Flynn, CNM. PhD, is the General Director of the Family Health and Birth Center which provides prenatal, birth, postnatal, gynecological and primary health care to underserved women and their families in Washington, D.C. Recently Cynthia served as Associate Professor of Nursing at Seattle University. There she not only taught, but remained in full scope clinical midwifery practice at Valley Medical Center where she cared for pregnant and birthing women, and practices well-woman gynecology, family planning, and treatment of sexually transmitted diseases.

Cynthia founded Columbia Women's Clinic and Birth Center, where she took care of pregnant women and infants up to two weeks of age and attended both birth center and hospital births. Before Cynthia earned her CNM, she worked as a registered nurse in labor and delivery and postpartum and is a certified Doula and Doula trainer.