Objective: To estimate the risk of stillbirth in apparently uncomplicated monochorionic-diamniotic twin pregnancies by systematic review and meta-analysis and compare it with that in uncomplicated dichorionic pregnancies.
Data sources: We performed an electronic search (January 1985 to April 2012) of Medline, PubMed, Embase, and ClinicalTrials.gov databases.
Methods of study selection: Studies detailing gestational-age specific stillbirth rates after 24 weeks of gestation in monochorionic-diamniotic twin pregnancies uncomplicated by twin-twin transfusion syndrome, growth restriction, or major anomalies. The rate and risk of stillbirth were calculated in 2-week gestational age blocks and compared in controlled studies with dichorionic pregnancies.
Tabulation, integration, and results: We evaluated 361 studies to include nine informative studies, four after additional data from the investigators. The rate of stillbirth per 1,000 uncomplicated monochorionic-diamniotic pregnancies at 32-33, 34-35, and 36-37 weeks of gestation was 5.1, 6.8, and 6.2, respectively. The risk of stillbirth per pregnancy at 32, 34, and 36 weeks of gestation was 1.6%, 1.3% and 0.9%, respectively. Compared with uncomplicated dichorionic pregnancies, the odds ratio for stillbirth per pregnancy at 32, 34, and 36 weeks of gestation was 4.2 (95% confidence interval [CI] 1.4-12.6), 3.7 (CI 1.1-12.0), and 8.5 (CI 1.6-44.7), respectively.
Conclusion: Uncomplicated monochorionic twin pregnancies are at substantial risk of stillbirth throughout the third trimester, which is severalfold higher than in dichorionic twin pregnancies. Given the risk of fetal death to the cotwin, these data should inform decisions around timing of delivery in seemingly normal monochorionic twin pregnancies.