You wouldn't believe how many times I get asked if my twins are identical. It isn't quite as common now that they are 3 but still common enough and every time I get asked this, I am dumbfounded. I have boy/girl twins. They can't be identical. It is absolutely impossible. Well, impossible except for a chromosomal mutation that can occur during development. Yes...I am 100% positive they are not identical. They are fraternal twins. I am sure.
Here is a brief biology lesson for any of you out there confused by identical and fraternal twins. Please note I have absolutely no medical background or training. I am just a mom who has been through a bunch of fertility treatments and been pregnant with twins three times Crazy I know. Twice with fraternal twins and once with identical, monoamniotic twins. Monoamniotic twins are a rare type of identical twin that share the same amniotic sac. Now as you may know, I don't have three sets of living twins. We lost one of the first set of fraternal twins very early in the pregnancy, around 6 weeks. We lost the set of identical twins around 12 weeks.
So...Identical Twins
Identical twins are just that...Identical. They come from one fertilized egg (one egg fertilized by one sperm) that splits into two embryos in the first few days after fertilization. They are called monozygotic in medical circles meaning they come from one zygote (fertilized egg). They are genetically identical and therefore are always the same sex. Either two girls or two boys. Identical twins are not hereditary. They are a spontaneous, random occurrence. The odds of having identical twins is approximately 3 out of 1000 births. Most identifical twins do not share an amniotic sac or a placenta. My identical twins were monoamniotic which meant they shared an amniotic sac and placenta but had two separate umbilical cords. This occurs 1 in every 35,000 to 1 in every 60,000 pregnancies. Monoamniotic twins are at a higher risk for complications and fetal death that singleton or other identical twin pregnancies.
So here is an early ultrasound photo of my set of identical, monoamniotic twins. The two gray blobs labeled a and b are the two babies. The elongated black oval surrounding both of them is the single amniotic sac they shared.
Now for Fraternal Twins
Fraternal twins are called dizygotic, meaning they are the result of two separate eggs fertilized by two separate sperm. Fraternal twins share about 50% of their DNA which is the same as any other siblings born at separate times. Fraternal twins can be the same sex or opposite sexes, although boy/girl twins are . So that means you can have two girls or two boys that are fraternal twins or boy/girl fraternal twins. Fraternal twins are twice as common as identical twins. Your chances of having fraternal twins is influenced by a number of factors including genetics (on the mother's side), maternal age, and fertility treatments.
Here is an ultrasound photo of my fraternal twins, Ella & Harrison. Again the gray blobs are the two babies. In this picture you can clearly see each baby has its own black circle or amniotic sac surrounding it.
Just to give John David and his twin equal time, here is a very early ultrasound picture of my first set of fraternal twins. Only one of these babies made it. If we hadn't been doing fertility treatments and had an ultrasound as soon as the pregnancy test came back positive we never would have known there were two babies. They look like little eye balls in there.
Although multiple pregnancies are more common today than in the past I guess the sight of twins or other multiples out in public grabs people's attention. I get stopped a lot when I am out in public by people asking questions about my twins. Are they identical? Nope. Do twins run in my family? Sort of. There are fraternal twins on both my side and my husband's side of the family. The fraternal twins in my husband's family have zero influence over my getting pregnant with fraternal twins though. And the fraternal twins in my family are my grandparents and great-grandparents generation. Are they "real" twins? I think people are asking if I went through fertility treatments to have my twins with this question. And the answer is yes. Yes I was going through fertility treatments when I got pregnant with Ella and Harrison. But Yes, they are real. I don't think fertility treatments makes them any less "real." They were still conceived at the same time, spent 37 weeks growing together inside me, and were born at the same time. I think that makes them "real" twins whether or not we had help having them or not.
So there is your biology lesson for the day. Hope you enjoyed it. And I apologize for the quality of the ultrasound photos. Ultrasound photos are the best anyway and then trying to scan them into the computer didn't help. They were the best I could do.
Hope you have a great day!
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