When you tell people you’re expecting twins, or when people see you out and about with twins, one of the first questions they’ll ask is “Are they identical or fraternal?” (this question will be asked forever and ever, everywhere you go, for all of eternity!).

But did you know, it’s not quite that straightforward.

One placenta, two placentas, one sac, two sacs…?

When did the embryo split?

So, you’ve got two placentas and two sacs? You still may have identical twins!

Let’s get down to basics.

Types of Twins

The three main types of twins are DCDA (dichorionic/diamniotic – two placentas/two sacs); MCDA (monochorionic/diamniotic- one placenta/two sacs); and, MCMA (monochorionic/monoamnionic – one placenta/one sac often referred to as Momo).

MCDA and MCMA twins are identical and are formed from a single embryo (one egg fertilised by one sperm) that splits. Depending on the timing of that split as to whether there are one or two sacs.

DCDA twins occur when two eggs are released and these eggs are fertilised by two sperm. These twins are fraternal…EXCEPT…sometimes they’re not! Up to around 30% of same sex DCDA twins are actually identical! HOW? Well, these cheeky twins occur when a single embryo splits super early, resulting in two placentas and two sacs, but identical babies.

So, if you have same sex twins with two placentas and two sacs and they turn up looking the same, it might be worthwhile having zygosity testing to find out for sure.

But I only had one placenta, why aren’t my twins identical?

So, just to complicate things a teeny bit more, sometimes your two placentas can fuse together! What you’re looking are two DCDA placentas from my twin boys, which fused together during pregnancy. Not to be confused with one placenta from monochorionic twins.

Want to chat about your twin birth preparation? I offer one-on-one support via Skype or phone and I’d LOVE to help you navigate the sometimes tricky path to positive twin birth. Let’s chat.

Elyse Jamieson – Birth Doula, Educator, and Twin Mama