Monoamniotic twins: What is it and what are the risks?

My wife and I are having twins, and the doctor said they might be "monoamniotic." He also said there was only a 50 percent chance of both of the twins making it. Please tell us more about this condition.


Peg Plumbo CNM

Peg Plumbo has been a certified nurse-midwife (CNM) since 1976. She has assisted at over 1,000 births and currently teaches in the... Read more

Twins are either mono-zygotic or di-zygotic. In your case, mono-zygotic, a single fertilized ovum splits into two distinct individuals. These babies will be "identical twins" -- of same sex and genetically identical.

The incidence of this type of twinning is approximately four per 1,000 births. Unlike the fraternal type of twinning (di-zygotic), this type does not seem to vary depending on mother's age or how many children she has.

Some twins share the same amniotic sac and the same placenta (monochorionic and monoamniotic -- 1 in 25,000 to 1 in 60,000 pregnancies) -- and because of this, cord entanglement and compression become a very high risk. This can lead to an interruption in the blood flow to one or both babies where they may not receive enough nutrients or oxygen.

When there is no membrane between the babies -- a monoamniotic twin pregnancy -- there is a very high risk of cord entanglement and also twin to twin tranfusion syndrome. This represents a very high risk pregnancy and intensive monitoring and testing of the babies is required. At times, it is safer to deliver such babies early, some as early as they are viable (24 to 28 weeks). A good NICU is essential when considering the birth. 34 weeks is often considered "full term" for monoamniotic twins because of the cord risks outweigh the prematurity risks.

I would recommend that you seek out the care of an perinatologist, an obstetrician who specializes in the care of high risk mothers and pregnancies and concentrate on excellent nutrition during this pregnancy.

If you have been diagnosed with monoamniotic twins, you may find a support group helpful to answer your questions and listen to the stories of others in a similar situation. You may want to visit the Monoamniotic Monochorionic Support Site

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