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Mo/Mo Twins: Definition, Risks, And More

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What are Momo twins

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Do you want to know what are momo twins? The concept of twins isn’t new anymore. In fact, most parents these days choose to wish to have twins, given the fact that they’d have two little munchkins with identical baby clothes, diaper bags, strollers, etc. How cute is that?

Up until now, the biggest distinction that was made between twins is to know whether they’re identical or fraternal, creating a genetic mystery for you. However, there is one more rare yet complicated distinction between the twins, also known as monoamniotic twins/monochorionic twins, or simply the mo/mo twins.

Don’t know what are Mo/Mo twins? Are you confused? Intrigued? If yes, there is no need to worry now, as we at Parenthoodbliss have curated this article that will help you with all the answers that you might be looking forward to. So, sit back, grab your drink and continue drinking!

First Things First, What Are MoMo Twins or Monoamniotic Twins?

Mo/mo or monochorionic/monoamniotic twins in twin pregnancies are those who share both – the chorionic and amniotic sacs in the mama bear’s belly. In other words and simpler terms, as mono literally translates to “one,” a mo/mo pregnancy is where there is only one placenta and a single amniotic sac that the two babies share.

To help you simplify and understand how the mo/mo twins in a twin pregnancy are different from identical and fraternal twins, we have made a distinction in the session below:

1) Identical Twins Or Monozygotic Twins -

Here, as the term itself gives it away, the twins are identical and come from the same fertilized egg. They are created when one egg and one sperm meet as expected. Shortly after fertilization, this single egg splits in two, resulting in these twins or as referred to as identical, because they share all the same chromosomes.

2) Fraternal Twins, Also Called As Dizygotic Twins -

Unlike the identical ones, a fraternal twin comes from two different eggs that are released closely together but fertilized by two different sperm. However, they share only 50 percent of their chromosomes, just like the other siblings with similar characteristics such as hair, eye color, or even gender.

Then what makes a monochorionic/monoamniotic twin? Believe it or not, twins are capable of sharing a lot more than just the chromosomes! Let’s understand it better:

3) Twins - Monoamniotic/monochorionic

When it comes to identifying the kinds of twins in a twin pregnancy, the classification generally depends on the fetuses if they have shared or separate chorionic and amniotic sacs. For a quick recap – the chorion is the outermost fetal membrane while the outer layer of it is known as the amniotic sac. Here, the chorion works to connect the amnion, amniotic fluid, and the fetus to the placenta.

Amnion, the innermost fetal membrane helps by protecting the fetus and also includes the amniotic fluid. Similarly, chorion, the outermost fetal membrane either shares an amnion or has one all of its own.

Note – Monoamniotic twins are identical or semi-identical twins who share the same amniotic sac in their mother’s uterus, with a shared placenta but two separate umbilical cords. On the other hand, monoamniotic triplets or monoamniotic multiples [4] are also possible, but again are extremely rare.

Fun fact – Irrespective of the twins sharing the same placenta, that is, the chorion for the pair, each can still have their own amniotic fluid, given if they have their own amniotic sac (i.e. two separate amnions).

Haven said that what then are the different combinations that are possible?

Three different combinations are possible; to name them: mo/mo, mo/di, di/di:

  • Di/di twins or dichorionic diamniotic – Here, each baby has its own individual chorion and individual amnion
  • Mo/di twins or monochorionic diamniotic – Where the twins share a chorion with separate amnion
  • Mo/mo twins – Here, they share one amnion and one chorion, in other words, everything is shared!

Note – In twin pregnancies, if the twins are fraternal, they’re di/di with their own little bubble and account for about 30 percent of identical twins. Depending on the time of the egg split, the identical twins can be either di/di, mo/di, or mo/mo, where, mo/mo is rather rare and accounts for only about 1 to 5 percent of all identical twins.

On the downside, the concerning part is that the more the twins share while in utero the higher the risk to the pregnancy.

Monochorionic Twins - How Are They diagnosed?

In twin pregnancies, especially if mo/mo, it is identified by ultrasound fairly early in the pregnancy, with the best ultrasound images for identification taken within the first 14 weeks of the pregnancy along with the visible placenta and amniotic sac.

In a mo/mo pregnancy, your ultrasound would show one placenta blood supply to two fetuses who appear in one amniotic sac, with no dividing membrane. On the other hand, the diagnosis is also possible if there is any evidence of umbilical cord entanglement and it’s best to have it diagnosed early so that the pregnancy may be closely monitored.

What Are The Risks Of Mo/Mo Twins Sharing The Same Amniotic Sac And Amniotic Fluid? - Medically Reviewed

Given any twin pregnancy, there is always an added pregnancy risk. With most revolving around intrauterine growth restriction – a fancy term of saying that there’s only so much room for two babies to grow!

Listed below are some of the complications/risks that are likely to take place with twins who share the mommies womb:

  • Placenta previa
  • Placental abruption
  • Placenta accreta
  • Prematurity
  • Low birth weight
  • Gestational diabetes
  • Gestational hypertension
  • Postpartum hemorrhage

AS for a mo/mo pregnancy, since the amount of amniotic fluid and almost everything is been shared, there are added risks. Here are the additional possible risks of a mo/mo pregnancy:

  • Premature delivery – In a mo/mo pregnancy, cesarean delivery is recommended by 32 weeks or 34 weeks to help reduce any risk
  • The difference in the birth weight – Given that the twins grow at unequal rates, there could be issues with one’s survival rate or the weight affecting the health inside the placenta
  • Concerns with the amniotic fluid – In case there is very little amniotic fluid, it could limit the size of the bladder size, as well as, the movement of the baby. However, on the other hand, too much amniotic fluid can also lead to an enlarged bladder that increases the chance of heart failure
  • Cord entanglement – With nothing to separate, the mo/mo twins have a risk of getting their umbilical cords tangled over time which could lead to extremely early twin deliveries. This is because the entangled umbilical cord could result in sudden death
  • Twin to twin transfusion syndrome (TTTS) – Twin transfusion syndrome is when the placenta is shared and has a risk of one twin sharing more blood volume and nutrients as compared to the other. In this case, monitoring is required as it could cause issues in both the babies with preterm birth or surgical repair in utero.
  • Twin reversed arterial perfusion sequence – This generally occurs in about 1 percent of mo/mo pregnancies, where one developed expectedly, while the other is mentally normal but without a functioning heart and many other body structures. Here, the babies are joined by a large blood vessel, therefore, the one without a heart receives all its blood from the pump twin, causing the pump twin’s heart to work much harder as compared to the otherwise normal condition. The larger the pump twin, the higher the likelihood of resulting in heart failure or death.

What Are The Treatments Available For A Mo/Mo?

Unfortunately, there is no way to prevent mo/mo twins. This is why the doctors then only focus on monitoring them closely, as soon as they are conceived, and be referred to as a high-risk pregnancy by your doctor.

Expect your health care provider to usually screen for abnormalities like TTTS and TRAP sequence, ask for frequent monitoring throughout the pregnancy, and depending upon the risk factors, have in-patient care.

Also, to prevent cord entanglement in a mo/mo pregnancy, expect to give birth via C-section and deliver early. So, make sure you are prepared with everything you need in your c-section hospital bag, even earlier, depending on the issue and condition.

To Conclude - Having Twins!

Irrespective of the fact of you expecting a twin, yourself being a twin, or are aware of twins, it’s rather fascinating to be aware of the processes that are involved in creating two humans at the same time! Isn’t it?

It not only helps you understand the different kinds, address risk, but also helps you take preventive action sooner that are caused in mo/mo pregnancies. Make sure to communicate with your doctor on a regular basis to ensure a healthy pregnancy.

What Are MoMoTwins FAQs

1) Why are MoMo twins dangerous?

Mo/mo twin pregnancies are known to be dangerous as they are susceptible to complications such as cord entanglement, intrauterine growth restriction, twin-to-twin transfusion syndrome, increased congenital anomalies, and increased perinatal mortality.

2) What are the risks of twins sharing one placenta?

The risk involved with twins sharing one placenta is the blood vessel connections that allow the fetuses to share a blood supply. This sharing of the blood supply could lead to uneven blood flow and volume that could threaten the growth and survival of either of the twins resulting in potential complications such as preterm birth and low birth weight.

3) Can MoMo twins survive?

Once you hit the margin of 24 weeks, the survival rate of MoMo twins goes from about 75 percent to 80 percent. That means the twins experience life-threatening complications as early as 26 weeks of pregnancy resulting in preterm delivery or C-section.

On behalf of the editorial team at Parenthoodbliss, we follow strict reporting guidelines and only use credible sources, along with peer-reviewed studies, academic research institutions, and highly respected health organizations. To learn about how we maintain content accurate and up-to-date by reading our medical review and editorial policy.

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