Monozygotic and Dizygotic?

Hello,

I was wondering, I see that some of you have mono/di twins, I was just wondering how is that possible? I thought that either the twins came from the same ovum (monozygotics) or from 2 separate ovi (dizygotics)... And also if you could please tell my how your OB determined this?

Thank you

Mag

 

Hi! The mono/di refers to Monochorionic Diamniotic. So yes, they are monozygotic twins (like you said from one zygote) that share one placenta (monochorionic) but have their own sacs (diamniotic). Its discovered via u/s. Sometimes its hard to tell if its only one placenta or two placentas fused but earlier on in the pregnancy its easier to tell and even throughout there are some indications - thickness of the membranes between them etc.

 

mono/di doesn't have to do with zygosity. it means that your twins are monochorionic/diamniotic - this refers to the number of placentas/amniotic sacs your babies have (in this case 1/2). mono/di twins, however, are always monozygotic. you can also have mo/mo twins (monochorionic/monoamniotic = 1/1) which are also always monozygotic. di/di twins (dichorionic/diamniotic = 2/2) can be monozygotic OR dizygotic. it's usually diagnosed early in pregnancy via u/s. although, sometimes two placentas that have fused together can be misdiagnosed as being a single placenta. it's important to know because there are potentially higher risks with mono/di & mo/mo twins & most doctors prefer to increase monitoring of the pregnancy. HTH!

 

My boys were mono/di. They shared a placenta, discovered at my 10 week u/s but had the own sacs. There membrane was also extremely thin

 

What they said ost:

 

My twin boys were mono/di. I won't repeat what everyone has told you but thought I'd share that mono/di twins are the most common identical twins. If the egg splits right away, you typically end up with two sacs, if the egg waits a little longer to split you typically end up with mono/di twins, and if it takes even longer it can be mono/mono twins (which is when they are in the same sac and share a placenta). Mono/di twins do share the same placenta but have a small membrane between them so that they aren't touching each other.

 

Thank you all so much!!! I understand now , then I think I have mono/di as they share the same placenta but they are separated by a membrane. The docs can't tell me though if they are identical or fraternal yet... The membrane seemed thin to me but I'm only a mom not an U/S expert... I have my next U/S in two weeks and I will be 21 weeks at that point, maybe we'll know more...But from you are telling me if they are mono/di they should be monozygotic... I don't know why the docs won't confirm that... They told me they are probably identical...

Thanks again!!

Mag

 

If they share a placenta, then they are identical, unless for some reason they think there were 2 placentas at once, and they fused.

 

what she said. :good: the only reason they aren't sure is because they haven't decided if there's only 1 placenta or 2 fused together. it's usually easier to tell at earlier ultrasounds & gets harder to tell the further along you are. if it's 1 placenta, then your twins are 100% for sure identical.

 

Thank you Rachel! For some reason, they are not sure... And I had an ultrasound at 8 weeks and all they talked about was the 2 fetuses they didn't mention at the time the placenta, everybody was so shocked I guess... But on the 12 week ultrasound, it only showed one placenta with a thin membrane separating the twins... Now they told me that we will probably know when they are born, patience, patience...

Thanks again!

 

Mine were mono/di... couldn't tell about the placenta until after birth and the lab confirmed it was just 1. I still had them DNA tested becuase my OB and the NICU MD's wouldn't say for sure they were ID even though they were mono/di. The DNA test confirmed ID.