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MoMo twins: Rare twist with twins creates unusual complication before birth

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Rachael's babies are what's called monoamniotic monochorionic, or MoMo twins.{ } They share a single amniotic sac, with separate umbilical cords connected to a shared placenta. (KOMO News){ }

KIRKLAND--When Rachael and Art Simpson were ready for their two year old daughter Ruben to be a big sister, they were excited to have their first ultrasound.

"It was a big emotional day for us," Rachael said.

The emotion came from not just discovering one little girl. They learned they were having twins. And moments later, they also learned about a rare complication.

"It was extremely stressful," Rachael said. "Everything's out of your hands. There's nothing you can really do at that point. You just have to hope for the best."

Rachael's babies are what's called monoamniotic monochorionic, or MoMo twins. They share a single amniotic sac, with separate umbilical cords connected to a shared placenta.

"The babies can swim around each other as they're developing and create these really amazing tangles and kots in their cords," Dr. Martin Walker explained. "When it's in a knot like this, you can imagine it can be pulled tight just by some chance movement of the baby."

And if the cords are too tightly knoted, the babies will both lose their blood supply, dying within minutes.

"For that reason, about 40% of these babies don't even make it to 24 weeks. They die in utero before they could get to the point where they could possibly survive. There's nothing you could do about it," Dr. Walker said.

But once a mom is 24 weeks into her pregnancy, the babies are considered survivors and old enough for mom to have an emergency cesarean section if the knotted cords pull too tight. Rachael hit that mark and has been on constant monitoring at Evergreen Health ever since.

"We're just really ready to meet them and start the next chapter," she said.

Once the babies are born, they'll spend at least a month in the hospital.

Just one percent of naturally conceived twins are MoMo twins. As rare as that is, another local couple hit even longer odds. Their triplets were born Thursday at Swedish Medical Center. Justin and Connor are MoMo brothers who shared a single amniotic sac, growing alongside their triplet sister, Anna. Mom and babies are all doing well.



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