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Unequal placental sharing is associated with inter-twin size discordance, twin-to-twin transfusion syndrome (TTTS) and reduced infant survival in monochorionic twin pregnancies. This study explores if inter-twin differences in impedance to blood flow (IDIBF) in the umbilical arteries influences infant survival in TTTS.
All women who underwent laser ablation of placental anastomoses for the management of TTTS between January 2012 and May 2018 at a single institution were included. Laser surgery was performed in all cases with Quintero stages II or greater and in women with Quintero stage I with either symptomatic polyhydramnios, cervix shortening or preterm labor. IDIBF in the umbilical arteries was estimated by substracting the pulsatility index (PI) of the umbilical artery of the donor twin from that of the recipient twin, prior to surgery. Outcomes included dual infant survival or survival of at least one fetus at delivery and at 30 days of age. Logistic regression analyses were perfomed to determine the relationship of IDIBF in the umbilical arteries with the study outcomes, while controling for gestational age (GA) at surgery, GA at delivery, Quintero stage, cervical length prior to surgery, inter-twin size discordance ≥25% and/or EFW<10 percentile for GA, advanced maternal age (≥35 years old), maternal obesity (BMI>35), and number of placental anastomoses.
A total of 230 consecutive TTTS cases met study the inclusion criteria. TTTS Quintero stages I, II, III and IV were present in 10%, 31.3%, 50.9% and 7.8% of all cases, respectively. Inter-twin size discordance ≥25% and/or EFW<10 percentile for gestational age was present in 72.4% of cases. Two live births or at least one live birth was present in 68.3% and 88.3% of cases, respectively. Two infants or al least one infant was alive by 30 days in 70.8% and 96.4% of cases, respectively. 27% (n=62) were lost to follow-up by 30 days or have not reached this age yet. Logistic regression analysis demonstrated that IDIBF in the umbilical arteries is an independent factor for the survival of one (p=0.004) or both infants (p<0.001) at birth as well as for the survival of both infants at 30 days of age (p=0.01). In contrast, neither Quintero staging nor inter-twin size discordance were associated with these outcomes (see Table).
Differences in impedance to blood flow in the umbilical arteries may influence infant survival in TTTS cases following laser ablation of placental anastomoses.