When we share with someone that we are having twins the first question is often:
" are they identical or fraternal?"
Our babies are fraternal.
When they were diagnosed as fraternal I quickly found out that a lot of what I knew about twins was not correct.
Now that we have twins on the way I have been doing LOTS of reading and feel like a semi-twin expert :) So, I thought I would start blogging a little bit about what I have learned, starting with the most basic of all "twin questions."
Since our babies are fraternal, I will talk about
Fraternal Twins first.
Fraternal twins are also known as dizygotic twins, which
means "from two eggs."
They are no more genetically similar than any two siblings would normally be. It is basically, as my doctor put it, "two for one"-two pregnancies in one! Nice.
And this is where I find a lot of people are mixed up (including myself): Fraternal twins are
what runs in families.
It is something your carry in your genetics.
I, however, I am still not sure who passed this oh-so-special gift along to my ovaries :)
They could be any combination of:
Girl-Girl
Boy-Girl
Boy-Boy
And as my math savvy husband has told me, we have a
25% chance of having Girl-Girl twins
25% change of having Boy-Boy twins
50% chance of having Girl-Boy twins
And, now a little about Identical Twins.
Identical twins are the result of one fertilized egg that has split into two identical copies of itself. They are also known as monozygotic twins, meaning "from one egg."
Identical twins share the exact same set of genetic material, and are (almost always) the same sex. Yes, there have been, in very rare cases, sets of identical boy-girl twins! Go google that one for yourself :)
Identical twins are just kind of a "fluke." It can happen to anyone!
Well, there you have it. A little bit about the differences between identical and fraternal twins.
Twins (of both kinds) occur in about 3.1% of births in the United States every year. That percentage is growing, largely in part to the use of Invitro-Fertilization. Andrew found some statistics that showed that "naturally occurring" twin pregnancies are very rare, making up less than 1% of all births in the US. Looks like we hit the jackpot :)