Perinatal outcome of monochorionic diamniotic twin pregnancy complicated by selective intrauterine growth restriction according to umbilical artery Doppler flow pattern: single-center study using strict fetal surveillance protocol.

Objective: To determine the perinatal outcome of monochorionic diamniotic (MCDA) twin pregnancies complicated by selective intrauterine growth restriction (sIUGR), which were classified according to the umbilical artery (UA) Doppler flow pattern of the IUGR twin.

Methods: This was a retrospective cohort study of all MCDA twin pregnancies diagnosed with sIUGR and managed at a single tertiary referral center between 2012 and 2018. Cases were classified according to the UA Doppler flow pattern of the IUGR twin as Type I (positive end-diastolic flow), Type II (persistently absent/reversed end-diastolic flow) or Type III (intermittently absent/reversed end-diastolic flow). Patients with Type-II or -III sIUGR were hospitalized at 26-28 weeks of gestation for increased fetal surveillance. Perinatal and immediate and long-term neurodevelopmental outcomes were stratified according to the UA Doppler flow pattern at the final examination. Intact survival rate was defined as the number of infants surviving without neurological impairment, divided by the total number of fetuses. Composite adverse outcome, defined as any mortality, presence of severe brain lesions on postnatal transcranial ultrasound or severe neurological morbidity, was also assessed.

Results: Of 88 MCDA twin pregnancies with sIUGR included in the study, 28 underwent selective termination by cord occlusion using radiofrequency ablation, resulting in a perinatal survival rate of 89.3% and a median gestational age (GA) at delivery of 33.8 (interquartile range (IQR), 28.8-38.2) weeks for the large cotwin. Expectant management was employed in 60 cases. In 26 (43.3%) cases in the expectant-management group, the classification according to the UA Doppler flow pattern changed during gestation, resulting in 26 (43.3%) cases of Type-I, 22 (36.7%) cases of Type-II and 12 (20.0%) cases of Type-III sIUGR at the final examination. The perinatal survival rate of both twins with sIUGR Types I, II and III at the final examination was 100%, 81.8% and 75.0%, respectively (P = 0.04). Two cases of double fetal death and one case of single fetal death occurred 1-4 weeks after the Doppler pattern had changed from Type I or Type II to Type III. The median GA at delivery was 34.8 (IQR, 33.1-35.7) weeks in Type I, 30.3 (IQR, 28.6-32.1) weeks in Type II and 32.0 (IQR, 31.3-32.6) weeks in Type III (P < 0.01). The total intact survival rate was 100% for Type I, 77.3% for Type II and 75.0% for Type III (P < 0.001). Multivariate analysis demonstrated that early GA at diagnosis (odds ratio (OR), 0.83 (95% CI, 0.69-0.99); P = 0.04) and the presence of Type II or III vs Type I at the last examination (OR, 13.16 (95% CI, 1.53-113.32); P = 0.02) were associated with preterm birth < 32 weeks' gestation. Early GA at diagnosis was also associated with the composite adverse outcome (OR, 0.60 (95% CI, 0.36-0.99); P = 0.04).

Conclusions: The classification system of MCDA pregnancy complicated by sIUGR, according to the UA Doppler flow pattern of the IUGR twin at final examination, is associated with perinatal outcome. Importantly, the UA Doppler flow pattern can change during gestation, which has an impact on the risk of fetal death. Nevertheless, under strict fetal surveillance, the perinatal outcome of these pregnancies is favorable. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.