Impact of cord entanglement on perinatal outcome of monoamniotic twins: a systematic review of the literature

Objective To review the current literature concerning perinatal outcome of monoamniotic pregnancies with cord entanglement. Methods A search in PubMed, EMBASE and MEDLINE for articles published between January 2000 and December 2011 was performed, using the following keywords: monoamniotic/monochorionic pregnancy(ies); twins; cord entanglement; fetal ultrasound/surveillance. Inclusion criteria for the study were: monoamniotic twins with documented cord entanglement at delivery, and perinatal outcome reported as proportional rates. Exclusion criteria were: higher-order multiple pregnancy; selective feticide; presence of twin reversed arterial perfusion sequence; conjoined twins; fewer than four cases in the series; and non-English language publication. Survival rates were stratified for method of prenatal management, sonographic diagnosis of cord entanglement and delivery mode. A meta-analysis was also performed using data from articles that stratified outcome according to the presence or absence of cord entanglement at birth. Comparison between neonates with cord entanglement and controls was deemed significant if the 95% CI of the pooled odds ratios did not encompass 1. MOOSE (Meta-analysis Of Observational Studies in Epidemiology) guidelines were followed. Results Nine articles met the inclusion criteria for this review, including a total of 114 monoamniotic twin sets (228 fetuses) with cord entanglement. The overall survival rate was 202/228 (88.6%). Perinatal mortality occurred in 26 (11.4%) fetuses; of these, 17 (65%) died in utero and nine (35%) died at birth. Five neonatal deaths occurred as a result of prematurity, two were related to structural abnormalities and two were caused by cord entanglement. Sonographic visualization of cord entanglement did not improve outcome. Four articles were included in the meta-analysis, with no significant difference in mortality between controls (n=66 fetuses) and twins with cord entanglement (n=82 fetuses), and higher morbidity in controls. Conclusions Cord entanglement does not contribute to prenatal morbidity and mortality in monoamniotic twin pregnancies.