Outcome of monochorionic twin pregnancy with selective intrauterine growth restriction according to umbilical artery Doppler flow pattern of smaller twin: systematic review and meta-analysis

Objective: To explore the outcome of monochorionic twin pregnancies affected by selective intrauterine growth restriction (sIUGR) according to the umbilical artery Doppler pattern of the smaller twin. Methods: An electronic search of MEDLINE, EMBASE, CINAHL and ClinicalTrials.gov databases (2000–2016) was performed. sIUGR was defined as the presence of one twin with an estimated fetal weight and/or abdominal circumference < 10th or < 5th percentile and classified according to the umbilical artery Doppler flow pattern of the smaller twin (Type I: persistently positive; Type II: persistently absent/reversed; Type III: intermittently absent/reversed). Primary outcomes were perinatal mortality, intrauterine death, neonatal death and double fetal loss. Secondary outcomes were neonatal morbidity, including abnormal postnatal brain imaging, intraventricular hemorrhage, periventricular leukomalacia, admission to neonatal intensive care unit and respiratory distress syndrome, deterioration of fetal status, gestational age at delivery and degree of birth-weight discordance. A composite adverse outcome, defined as the presence of any mortality or abnormal brain findings, was also assessed. Quality assessment of the included studies was performed using the Newcastle–Ottawa Scale. A random-effects meta-analysis was used to compute the summary odds ratios (ORs), mean differences (MD) and proportions for the different outcomes. Results: Thirteen studies (610 pregnancies) were included. The risk of perinatal mortality was higher in twins affected by Type II compared with Type I sIUGR (OR, 4.1 (95% CI, 1.6–10.3)), whereas there was no difference among the other variants of growth restriction. Risk of abnormal postnatal brain imaging was significantly higher in twins affected by either Type II (OR, 4.9 (95% CI, 1.9–12.9)) or Type III (OR, 8.2 (95% CI, 2.0–33.1)) sIUGR compared with Type I sIUGR. The risk for neonatal intensive care unit admission was higher in Type II compared with Type I sIUGR (OR, 18.3 (95% CI, 1.0–339.7)). Twin pregnancies affected by Type I sIUGR were delivered at a significantly later gestational age compared with Type II (MD, 2.8 (95% CI, 1.83–3.86) weeks) and Type III (MD, 2.1 (95% CI, 0.97–3.19) weeks). The degree of birth-weight discordance was higher in Type II compared with Type I (MD, 21.6% (95% CI, 9.9–33.2%)) and Type III (MD, 9.3% (95% CI, 3.8–14.9%)) sIUGR. Conclusion: Monochorionic twin pregnancies affected by Type II sIUGR are at a higher risk of perinatal mortality and morbidity compared with Type I. The likelihood of an abnormal outcome is usually not significantly different between sIUGR Types II and III, although the latter has an unpredictable clinical course.