Sunday, June 28, 2009


One question we seem to get over and over is whether our boys are identical twins. We have varying answers to this seemingly straightforward question, depending on how much we like the asker. Just kidding. But the answer definitely does vary with the context. If you are reading this, you are getting "the long answer." The short answer is "yes."

First, here's some background on twins . . . fraternal twins are essentially siblings born on the same day. They are the result of two separate eggs that happen to be released at the same time, which are then fertilized by two separate sperm (sorry for the biology lesson, but it will get worse from here on out). Fraternal twins tend to run in families, since it is related to the tendency of the woman to drop multiple eggs. Fraternals are more common in certain races (blacks are more likely, Asians less likely to have twins), older women, and those who use IVF or other forms of assisted reproduction. As a result, fraternals used to occur in about 1 in every 90 births. In the past 20 years, that number has doubled to about 1 in every 40 births. If you live in L.A. or NYC, where affluent, older women are increasingly tending to undergo assisted reproduction, you might think that there was a sale at Penney's on (fraternal) twins.

By contrast, identical twins are a completely random phenomenon in which one egg is fertilized by one sperm and then the egg splits within a few days after fertilization. Therefore, identical twins are carbon copies of each other. Identical twinning is a spontaneous thing that occurs at a rate of about 1 out of every 300 births, the world over.

When we had our very first ultrasound, at which we were told there were two babies brewing in there, the doctor assessed the placental biology and told us we were likely having identical twins. This was because it looked like we had two amniotic sacs sharing a single placenta (again, sorry for the biology lesson). This is the biology in about 70% of identical twins. However, what looks like a single placenta can actually be two placentas "fused" into one. Therefore, a pathologist looks at the placenta post-partum.

All of this is very boring, I know, so I'll cut to my point: three doctors told us we had identical twins, but we dug a little deeper and determined that it's really only a "best guess." The only way to know, with certainty, that they are identical is to a DNA test, something that insurance doesn't pay for and most people never do.

I know if I asked my (doctor) dad about identicality, he would say, "Look at them." I don't know. You tell me- identical or not?


Goddess in Progress said...

It's incredible how many times I've wanted to spell out that lesson for people. Especially the ones who ask if my b/g twins are identical, or if twins run in my husband's side of the family. :-)

Alberta said...


Winge said...

I think, vadlo biology cartoons has some good twin cartoons!

Marianne said...

I vote identical. And extremely cute.