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What is monoamniotic twins?
What percentage of twins are monoamniotic?
Are monoamniotic twins common during pregnancy?
Are monoamniotic twins dangerous?
Do monoamniotic twins have a placenta?
What are the different types of twin pregnancies Besides monoamniotic?
Monoamniotic twins develop when an embryo does not split until after formation of the amniotic sac, [1] at about 9–13 days after fertilization. [3] Monoamniotic triplets or other monoamniotic multiples [4] are possible, but extremely rare. [1]
Oct 14, 2024 · Monoamniotic (Mo-Mo or mono-mono) twins share both a placenta and amniotic sac; Monochorionic twins are more typical when it comes to identical twins, while monoamniotic twins are very rare. But dichorionic twins are the most common type of twins overall, because they can be fraternal or identical.
- Karen Miles
Jul 14, 2023 · With less room to grow, twin pregnancies usually result in preterm birth. However, monoamniotic twins face additional risks because they share a single placenta and amniotic sac.
What is a monoamniotic twin pregnancy? This is a type of twin pregnancy defined by the presence of a single shared placenta between the two fetuses and a single shared amniotic sac. How does a monoamniotic twin pregnancy happen? It is a rare condition that happens in about 1 per 10,000 pregnancies.
- Overview
- What are mo/mo twins?
- How are mo/mo twins diagnosed?
- What are the risks of mo/mo twins?
- What treatments are there for mo/mo twins?
- Takeaway
In most cases, the biggest distinction people make between twins is whether they’re identical or fraternal (and even that separation can be confusing for some).
If up until this point twins have been a genetic mystery for you, please allow us to introduce you to some of the various types of twins. One of the most rare and complicated types are sometimes called mo/mo twins. Confused? Intrigued? Keep reading to find out more!
Mo/mo is a shortened form of monochorionic monoamniotic. Mo/mo twins are those who share both the chorionic and amniotic sacs.
Or to put it another way, since mono means “one,” a mo/mo pregnancy is one where there is one placenta and one amniotic sac for both babies.
Confused about how this works? Allow us to back up a bit…
Most people have heard mention of identical and fraternal twins before, right?
•Identical twins (also called monozygotic twins) come from the same fertilized egg. They are created when one egg and one sperm meet as expected. Shortly after fertilization, the single egg splits in two. These twins are referred to as identical, because they share all the same chromosomes.
•Fraternal twins (also called dizygotic twins) on the other hand come from two different eggs that are released close together and fertilized by two different sperm. They share only 50 percent of their chromosomes as other siblings do, and characteristics like hair and eye color or gender can be the same or different.
Mo/mo twins are typically identified by ultrasound fairly early in the pregnancy. The best ultrasound images for this identification happen within the first 14 weeks of the pregnancy when the placenta and amniotic sac are more visible.
For a mo/mo pregnancy, the ultrasound will show one placenta supplying blood to two fetuses. Both will also appear within the same amniotic sac, with no dividing line between them.
Any time someone is pregnant with twins there are additional pregnancy risks. Many revolve around intrauterine growth restriction, which is a fancy way of saying that there’s only so much room for two babies to grow!
Some complications that are more likely with a twin birth include:
•placenta previa
•placental abruption
•placenta accreta
•prematurity
There is no way to prevent mo/mo twins, so doctors focus on monitoring once they are conceived, and you can expect to be referred to an OB-GYN who specializes in high risk pregnancies.
Your doctor will usually screen for abnormalities like TTTS and TRAP sequence and ask that you continue frequent monitoring throughout the pregnancy.
Depending on a particular pregnancy’s risk factors, you may require in-patient care with continuous monitoring after a certain point in your pregnancy.
To protect complications like cord entanglement, mo/mo twins are frequently born via C-section and delivered early.
Whether you are a twin, are having twins, or just know twins, it’s fascinating to think about the processes involved in creating two humans at the same time!
For those expecting twins, understanding twin types can help to identify and address risk for issues caused by mo/mo pregnancies.
- Catherine Crider
Monoamniotic twins occur when a single fertilized ovum (egg) results in identical twins that share a common placenta and amniotic sac. Monoamniotic twins are very uncommon, representing approximately one percent of identical twins and less than 0.1 percent of all pregnancies.
Feb 5, 2019 · Monoamniotic twins are very rare, with a prevalence of only 8 per 100 000 pregnancies (multiples and singletons combined); they account for fewer than 1% of all twin pregnancies 1. Their complication rates, on the other hand, are extremely high.
