Answer

We present a case of cord entanglement. Unfortunately, the pregnancy ended in fetal demise two weeks after our exam. 

Discussion

Monochorionic monoamniotic pregnancy represents the rarest type of multiple gestation, accounting for approximately 1% of all twin pregnancies. The risk of fetal mortality in this type of pregnancy is around 80%. In the case of twin pregnancies, the fetuses share a common placenta, amnion, and chorion. The chorionicity and amnionicity are determined by the timing of zygote division. If the zygote divides between days 8 and 12, a monochorionic monoamniotic pregnancy results. A specific complication uniquely associated with monoamniotic and monochorionic pregnancy includes conjoined twins and cord entanglement.

Cord entanglement can be visualized from the 12-13 weeks of pregnancy. The risk of cord events increases in cases of close cord insertion on the placenta. Some studies have confirmed that intermittent occlusion is associated with neurological morbidity, while prolonged occlusion is fatal. Ultrasound may visualize intertwined umbilical cords. On Doppler flow studies, intermittent or persistent notching of the umbilical artery may be present. This phenomenon is typically observed in abnormal uterine artery flow associated with placental insufficiency and is less frequently seen in umbilical artery flow disorders. Based on physical calculations, it has been shown that notching does not occur unless there is a reduction in tube diameter below 75%. Therefore, notching is present in cases of significant flow reduction.

Proper management with close monitoring of fetal condition and early delivery can reduce perinatal morbidity. However, due to the risk of sudden fetal death, it is essential to provide parents with clear and honest information.

References
[1]  Hack KE, Derks JB, Schaap AH, et al. Perinatal outcome of monoamniotic twin pregnancies. Obstet Gynecol. 2009 Feb;113(2 Pt 1):353-60.
[2]  Arabin B, Laurini RN, van Eyck J. Early prenatal diagnosis of cord entanglement in monoamniotic multiple pregnancies. Ultrasound Obstet Gynecol. 1999 Mar;13(3):181-6.
[3] Overton TG, Denbow ML, Duncan KR, Fisk NM.  First-trimester cord entanglement in monoamniotic twins. Ultrasound Obstet Gynecol. 1999 Feb;13(2):140-2.
[4] Dias T, Mahsud-Dornan S, Bhide A, et al. Cord entanglement and perinatal outcome in monoamniotic twin pregnancies. Ultrasound Obstet Gynecol. 2010 Feb;35(2):201-4. 
[5]  Van Mieghem T, De Heus R, Lewi L, et al. Prenatal management of monoamniotic twin pregnancies. Obstet Gynecol. 2014 Sep;124(3):498-506.

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