Baby A and Baby B expected in early June 2004


What is MOMO Twins?

The fetuses are in the same sac with no separation between them. That means that they float freely around each other, twist their cords and risk suffocating each other. This is a rare situation (1% of all pregnancies are twins and 1-2% of all twins are in the same sac like this) and high-risk.

This condition is called monochorionic (one placenta) and monoamniotic (one sac). Needless to say that this is just 1 step before siamese or conjoined twins. It's common to have only one placenta with each baby in his own sac inside of the placenta. That's called monochorionic and diamniotic. In our case it's only one sac. This condition is also called MoMo twins, for short.

How does it happen?

1. Singleton Pregnancy. When the egg and sperm meet, an embryo is formed, and it later on develops into one baby.

2. Fraternal Twins. Sometimes there are two eggs that meet two sperm, and 2 embryos are formed. These are called fraternal twins.

3. Identical Twins. Sometimes, the embryo decides to split. Nobody knows why that happens. When the split occurs, it's called monozygotic (one egg) and identical, since the twins share the exact same genetic code. If it happens within a day or two after conception, then it splits completely and forms 2 placentas and 2 sacs, which will later develop into twins. This is called dichorionic and diamniotic. If this splitting occurs a little bit later on, within 3-5 days, the placenta around the embryo has already started to form. At that point, the 2 halves of the embryo are stuck inside of the same placenta, but they still develop their own inner sacs around them, or a membrane between them. This is very common for identical twins and it's called monochorionic diamniotic. If the embryo decides to split 5-8 days after conception, then there is no membrane separating the fetuses, and that's when a monochorionic monoamniotic twin pregnancy occurs, in 1-2% of all twin pregnancies. After this, there is just one more possibility. If the embryo decides to split more than 10 days after conception, then it doesn't separate all the way and the result is conjoined or siamese twins.

What is our plan of action?

First we have to determine for sure that there are no obvious deformities and that the twins are not conjoined. We will have several ultrasounds and all kinds of other tests in the next few weeks. We will keep an eye out for the elusive membrane - it still may be there, just hard to see. Then we have to wait patiently until week 24 and hope that the babies survive at least that long. Until then there is nothing we can do - we can't restrict their movement.

Once they reach 24 weeks, they may survive outside the womb. At that point I will be monitored regularly at the hospital for any signs of distress. They will be looking for a drop in heartbeat in either baby - that would mean that they are tightening cords too much and that I would have to deliver immediately before they kill each other. Most likely this monitoring will be daily. If everything goes well and I reach around 30 weeks, I may go and stay at the hospital for constant monitoring. The later it gets in the pregnancy, the more chances are that the babies will tighten the cords, therefore momo twins are never full-term. They are always delivered by c-section before week 35 (of 40).

The risks of premature birth are a lot lower than the risks of cords tightening too much and cutting off nutrition to one or both babies. The earlier they are delivered, the longer they will have to stay at the neonatal intensive care unit (NICU) and the more problems they will have - underdeveloped lungs, brain bleeds, etc.

There are other risks of course. There are higher chances for abnormalities in momo twins, for twin-twin transfusion syndrome (TTTS) - that's when twins share a blood vessel in the placenta that supplies nutrition and therefore one baby receives more nutrition than the other and one doesn't fully develop in one way or another, etc.

So, at this point we take more tests, sit and wait. We try to eat right and exercise, but it's not easy with an all-day feeling of fatigue and frequent moments (or hours) of nausea. And we try to educate ourselves and not to worry.

We are optimistic and looking forward to doubling our family by next summer!

Here is a link to a momo support group with tons of information and great description of what is MOMO Twins can be found here.

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2004 by Julia Satovsky. All rights reserved.