Prolonged Intermittent Reversed End-Diastolic Flow in a Monochorionic Twin Pregnancy Associated with Twin-to-Twin Transfusion Syndrome and Absence of Hyrtl’s Anastomosis

Abstract

A 26-week twin pregnancy was diagnosed with twin-to-twin transfusion syndrome. The donor twin had reversed end-diastolic flow (REDF) on cord umbilical Doppler examination. This finding persisted for 2 weeks, with occasional Doppler findings of absent, as well as reversed, end-diastolic flow. Delivery was precipitated by the absence of growth in the donor twin and the deteriorating condition of the recipient twin. Pathologic examination of the placenta after delivery disclosed an unbalanced vascular communication between the twins and absence of Hyrtl's anastomosis in the umbilical cord of the donor twin.We postulate that the absence of Hyrtl's anastomosis effectively isolated the circulations of the two umbilical arteries, allowing REDF, a finding usually associated with imminent demise, to persist for 2 weeks without evidence of fetal distress.REDF is generally thought to be an immediate precursor of fetal demise, indicating extreme increased placental resistance. We report a case of REDF that persisted for a period of 2 weeks before delivery of a twin infant with intrauterine growth restriction, twinto-twin transfusion syndrome, and an absent Hyrtl's anastomosis at the insertion of the umbilical cord of the donor twin. Hyrtl's anastomosis is the normally occurring artery-to-artery shunt present at the placental cord insertion that equalizes the pressures within the cotelydonary systems fed by the two umbilical arteries. CASE REPORTMs. YC was a 16-year-old, gravida 1, para 0, receiving prenatal care for a twin pregnancy in Mexico until 26 weeks. She was referred for an ultrasound examination on transferring care to a local clinic at 26 weeks, at which time she had a 30-week symphysis-fundal height. The ultrasound examination revealed that Twin B had an average ultrasound age of 26 weeks and 6 Ϯ 14 days, and an estimated fetal weight of 1023 Ϯ 137 gm. Twin A was found to have a head circumference equivalent to 23 weeks and 1 day and an abdominal circumference equivalent to 20 weeks and 2 days, with an average ultrasound age of 22 weeks and 1 Ϯ 14 days and an estimated fetal weight of 419 Ϯ 56 gm. Both twins appeared anatomically normal. Severe oligohydramnios was noted around twin A, but the amniotic fluid volume was normal surrounding twin B. In addition, twin B had a pericardial effusion with the right atrium bigger than the left. There was a central cord insertion for twin B and a marginal cord insertion for twin A. Cord umbilical Doppler showed a systolic/diastolic flow ratio of 3.0 for twin B and REDF in twin A. A diagnosis of possible twin-to-twin transfusion syndrome was made, with twin A assumed to be the donor and twin B the recipient.The patient was admitted to hospital, betamethasone was given, and monitoring commenced. No abnormalities were noted on nonstress testing of both twins, and the patient was therefore managed expectantly. Biophysical profiles performed the next day were 8/8 for twin B and 6/8 for twin A (Ϫ2 for fluid). Later that day, twin A was re-evaluated by Doppler and no REDF was noted...

Incidence and characteristics of umbilical artery intermittent absent and/or reversed end‐diastolic flow in complicated and uncomplicated monochorionic twin pregnancies

“…The anatomical explanation for the development of iAEDF/iREDF in monochorionic twins may be the presence of large AAA. These have frequently been identified, either by color Doppler or placental examination, in the present series and in previously reported cases2–6. AAA represent the collision of two opposing blood flows3.…”

“…However, the existence of direct vascular connections between the cord insertions may generate other hemodynamic phenomena that to date have received little attention. The appearance of intermittent episodes of absent or reversed end‐diastolic flow in the umbilical artery (iAEDF/iREDF) of monochorionic twin fetuses was described in 1986 2 , and has later been confirmed in case reports and clinical series3–6. This phenomenon is characterized by the observation of several waveforms with absent, or even reverse, diastolic flow, followed only seconds or minutes later by a progressive recovery of diastolic flow resulting in one or more alternating patterns with a variable periodicity within the same examination (Figure 1).…”

The role of the absence of Hyrtl’s anastomosis in monochorionic pregnancy: Friend or foe?: A case report

“…However, the opposite result compared to the singleton placenta was obtained. Walker [ 5 ] reported a case of monochorionic twin pregnancy associated with SFGR and suspected twin-twin transfusion syndrome. Reversed end-diastolic flow, which is an immediate precursor of fetal demise, was noted at multiple sites in the umbilical cord of the smaller/donor twin on the day of hospital admission.…”