Twin A and B are mono-di twins, short for monochorionic-diamniotic. They split from a single egg three to seven days after conception. Each twin has her own umbilical cord and amniotic sac, but they share a placenta. It’s hard to tell when you’re looking at it on a fuzzy gray screen, but the whole thing looks like one of those cherries that is really two developed on the same stem but stuck firmly together.
Mono-di twins have a 1 in 7 risk of a condition called Twin-to-Twin Transfusion syndrome, a really scary complication where the blood vessels in the cord filter all the blood supply into one twin and then the other. One twin swells up and develops heart problems from all the extra pumping, and the other one shrivels up like a raisin because it can’t get enough blood. This condition is usually apparent by 18-25 weeks, so that explains the extra scrutiny. Thankfully, the girls measured about 20 weeks today and there wasn’t any difference in amniotic fluid, the first sign of TTTS.
We’ve been fielding questions about twins in the family since our discovery ultrasound two weeks ago. No, neither of us have twins in our lineage, but this makes sense. Family genetics can produce only fraternal twins, which are caused by more than one egg released at once. Fraternal twins are also the only kind produced by taking fertility drugs to induce hyperovulation, one reason why it seems like there are many more sets of twins than there used to be. Higher maternal age is another factor in increased chance of fraternal twins, but there is no way to predict or increase the likelihood of the spontaneous dividing of a single pregnancy that causes a set of identical twins, a 1 in 250 chance for everyone, no matter what.
The first thing I wanted to know about my very special girls at this ultrasound was their position. Right now they are both breech (imagine me with two hamster-sized fetuses perched upright on my lap). Now that they have their heads together, I hope they can figure out a way to go head down, because I am really hoping for a natural birth. There are complicated formulas for positioning combinations in a twin delivery, but my best chance of not getting popped like a beach ball in front of a hundred interns taking notes (UK is a teaching hospital) is for them both to be bottoms up at term.
We were also hoping for some cute two-heads-together or four-little-feet pictures, but our twins were not in a photogenic mood. The main reason the scan took over an hour was their constant movement. The tech would isolate a foot, prepare to measure it, and it would disappear. She could move the camera a bit, but the first foot that came into view might not be the right one of the four squirming feet she had to keep straight.
We did, however, get a “Power to the Babies!” sign from Twin B, busy executing a barrel roll.
Devon’s favorite postpartum gesture was to make a punctuating grunt and stab a fist emphatically in the air, like he was saying “Power to the Babies!” I think Twin B was just reminding us who was in charge.
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