A 30 year old G1P0 has division of a single fertilized oocyte at 10 days post fertilization. Ultrasound in the first trimester shows twins, a single placental disk, and no intertwin membrane. Instillation of dye in the amniotic sac of one twin is performed and amniotic fluid drawn from near the second twin has dye.
She is admitted at 26 weeks pregnancy and will stay as an inpatient until 32 weeks when she will get a C-section. When you ask why, the attending says, "We have to do daily fetal monitoring, look for cord knots on ultrasound, and check Doppler velocitometry."
Challenge: What is the concern, which is unique to this type of pregnancy?
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