This whole twin thing can be quite confusing, even to parents of twins. I wanted to give a guide and educate those on twins, because I, too, knew absolutely nothing about twins. If it weren’t for having them, I’d still probably be in the dark. While this post may be boring to some, I feel it’s a good idea to spread the knowledge.. I mean who knows.. maybe they’ll have twins one day, too 😉
Two most very important points to start:
- Boy/Girl twins are not identical. Why? One has a penis and the other has a vagina. They can look alike, but similarities does not mean identical! The only exception to this is a genetic defect (aka hermaphroditism and it’s called Turner’s Syndrome). And, this is very, very rare.
- Same sex does not mean they are identical! Unless you know the twins shared the same sac and placenta, the best way to know if twins are identical is if they have genetic testing.
There’s a lot of terms when you have twins (this I had no clue about prior to conceiving), so, here is some vocabulary for you and a diagram to follow along with:
- Monozygotic: one egg
- Dizygotic: two eggs
- Monoamnionic: one amniotic sac (bag of fluid that protects the baby)
- Monochorionic: one placenta (attaches to the uterus and umbilical cord, nourishes the baby aka the lifeline, and some people eat this after birth)
- Diamnionic: two amniotic sacs
- Dichorionic: two placenta
Further into terms:
- Momo (Monoamnionic/Monochorionic): one sac, one placenta (aka always identical!)
- Modi (Monoamnionic/Dichorionic): one sac, two placentas
- Didi (Diamnionic/Dichorionic): Two sacs, two placentas (boy/girl twins are didi twins)
Okay, so what is identical?
Identical twins: Identical twins stem from one egg that splits into two. This can happen at various points in the whole getting pregnant process, resulting in the different types of identical twins (momo, modi or even didi). The egg splitting completely spontaneous. There is some belief that genetics do have a role in why the egg splits, but there is no definitive proof to state that identical twins are genetic.
Then, what is fraternal?
Fraternal twins: Fraternal twins come from two separate eggs, meaning one or both ovaries popped out one too many eggs. Fraternal twins can be genetic (but not always). Fraternal twins are caused by the mother, aka hyperovulation. The hyperovulation gene tends to run in families, but it can be caused by a whole lot of other things!
What are some cool facts about twins?
- They can have different skin colors (See Kalani and Jarani Dean).
- Very improbable, but twins can have different fathers.
- They can be conjoined- this happens when the egg creating the twins doesn’t fully split.
- They don’t always share the same birthdate (See the most recent story in Delano of a mother giving birth to twins on Dec 31, 2017 and Jan 1, 2018).
Did you know these facts about twins?