Monochorionic Monoamniotic (MoMo) Twins

Monochorionic Monoamniotic (MoMo) Twins

A twin pregnancy is always more worrisome to the mother. If diagnosed with MoMo twins the pregnancy is a risky one. Simple facts and knowledge about the various risks involved can ensure that the mother-to-be understands what is happening, and is better able to decide with her doctor, the risks, and complications that could occur.

What are MoMo Twins?

MoMo twins mean Monochorionic (single egg covering sac) Monoamniotic (single amniotic sac or bag of water). It means that both the babies are in the same amniotic sac and have only a single covering egg sac or chorion. These twins are often called “mono mono identical twins”, and just about 1% of all twins are MoMo twins. The pregnancy is termed as a high-risk pregnancy.

Why do They Form?

When the egg and the sperm unite and become one, it is known as fertilisation. The resultant embryo is immediately covered with a chorion or egg sac to help protect the developing embryo. Twins occur when there are two embryos in the uterus due to a split. In the case of Monochorionic twins, the embryo, during the process of growing, emerges as two separate embryos each developing a placenta that connects to the mother’s uterus. If each embryo develops its own amniotic sac, it is called Diamniotic and two embryos will share the same egg sac while advancing in their sacs. However, when only one amniotic sac is present, both embryos grow in a single amniotic sac and a single egg sac covering and this leads to MoMo twins.

How are Mono-Mono Twins Diagnosed?

Ultrasound scanning is the only way to detect MoMo twins. High-resolution Ultrasound Doppler sound waves are used to study the growing foetus in real time. Your rare twin pregnancy needs aggressive monitoring and expert care of a perinatologist.

Risks and Complications Associated with Mono Chorionic Monoamniotic Twins

MoMo Twins

Almost all MoMo twin deliveries are premature deliveries. The twin foetuses connect to the placenta via their umbilical cords. It puts them at risk of several complications.

1. Cord Entanglement

Cord entanglement is a complication associated with monoamniotic twins who share a single amniotic sac. Since there is no amniotic membrane separating them, their umbilical cords could get entangled, cutting off the vital blood supply and nourishment to the growing babies. If the twins get entangled and tied together in the uterus, labour and delivery may be complicated as one of them could get stuck in the birth canal. This could endanger the life of the babies and cause foetal distress.

2. Cord Compression

As twins share the amniotic sac, there is a chance that they might press against the others umbilical cord while making internal movements. Prolonged pressure may cut off the blood supply and nutrients from travelling to the other baby, resulting in foetal death.

3. Twin-to-Twin Transfusion Syndrome (TTTS)

This syndrome happens if one twin receives the majority of the nourishment in the womb, causing the other twin to become undernourished. Diagnosis rests on comparing the physical development of both of the twins.

4. Preterm Birth

All monoamniotic twins are born prematurely because full-term pregnancy is risky and deemed unsafe due to the risk of cord entanglement and compression. Usually the twins are delivered by cesarean section after 34 weeks in the womb.

Many monoamniotic twins have to be delivered, sometimes as early as 26 weeks, depending on the risks involved. MoMo twins with a preterm delivery face many life-threatening conditions both in the womb and on being delivered.

Treatment for Monoamniotic Twins

High-resolution Doppler Ultrasound imaging which is a non-stress test will help assess the growth and identify potential cord problems. Such tests allow the doctor to study if it is necessary to intervene or deliver the babies, due to their cords getting entangled or compressed.

As the process of MoMo pregnancy is considered high risk, there is no other way than to deliver the babies in cases of complications. A perinatologist or an experienced twin delivery obstetrician should be consulted to weigh the risks of the pregnancy and whether there is any threat to the lives of the babies and mother-to-be.

Usually MoMo twins are delivered after 32 weeks and steroids administered to help their lung development after birth. A cesarean section is mandated for MoMo babies to avoid cord prolapse which occurs when the second baby’s cord is expelled as the first baby is delivered.

An experimental drug, Sulindac, has, of recent, been used to lower the amount of fluid in the amniotic sac. This is thought to reduce the amount of foetal movement, cord entanglement or compression. Study and research on the drug and its effects are still underway.

Aggressive foetal monitoring of the monoamniotic twins is a must throughout your pregnancy with bi-weekly control of foetal heart rate and movement after the 26th week. Hospitalization after the 28th week is advisable.

Other Facts about Mono-Mono Twins

Facts About Mono-Mono Twins

  • MoMo babies are always the same sex babies since the splitting of the same embryo forms them.
  • MoMo twins are very rare. Only 1% of twins are monoamniotic.
  • In early pregnancy and up to 24 weeks, the monochorionic twins have a low survival rate of 50%.
  • Sulindac is a drug that lowers the amount of amniotic fluid, thereby reducing the space that babies have to move around. The use of this drug needs further research and should be used with caution.
  • If you are dealing with MoMo multiples, try going to a perinatologist rather than your regular obstetrician. This is because MoMo twins are classified as ‘high-risk’ and would require a doctor who specialises in such type of pregnancies.
  • After 28 weeks of pregnancy, hospitalisation is advisable.
  • In early pregnancy, MoMo twins are often misdiagnosed because the separating amniotic membrane is fragile. Later ultrasound scanning reports could reveal a dividing membrane confirming a MoDi (Monochorionic, Diamniotic) pregnancy.

MoMo twin is a rare occurrence. Constant monitoring by an experienced obstetrician or perinatologist is recommended in a MoMo pregnancy.

Also Read: Twin Pregnancy Types