bean70's comments

10 Things to Know When You Find Out There's More than One! - Blog Entry

01 Apr 2007 05:46 PM

Hi Valerie - I just wanted to add to your number 1. If a sonogram shows two fetuses in one placenta, then they are most likely identical twins. Fraternal twins will most likely each have their own placenta, so you'll see two on the sonogram. Anomolies of this rule are very rare but do occur. For example, monozygotic (identical) twins can each have their own placenta, but that happens in less than 20% of identical twin pregnancies. And only on extremely rare occasions do fraternal twins share a placenta. As a matter of fact, there are only a few recorded instances of this ever happening, and it is usually with test tube fertilization. So if you see two fetuses in one placenta, you can be pretty much guaranteed that they are identical! And if you see two placentas, your chance of the babies being fraternal twins are pretty great. Which means that oftentimes, sonograms do give an accurate telling of whether twins are identical or fraternal.