• Fiona Cheong-See, Ewoud Schuit, David Arroyo-Manzano, Asma Khalil, Jon Barrett, K S Joseph, Elizabeth Asztalos, Karien Hack, Liesbeth Lewi, Arianne Lim, Sophie Liem, Jane E Norman, John Morrison, C Andrew Combs, Thomas J Garite, Kimberly Maurel, Vicente Serra, Alfredo Perales, Line Rode, Katharina Worda, Anwar Nassar, Mona Aboulghar, Dwight Rouse, Elizabeth Thom, Fionnuala Breathnach, Soichiro Nakayama, Francesca Maria Russo, Julian N Robinson, Jodie M Dodd, Roger B Newman, Sohinee Bhattacharya, Selphee Tang, Ben Willem J Mol, Javier Zamora, Basky Thilaganathan, Shakila Thangaratinam, and Global Obstetrics Network (GONet) Collaboration.
• Women's Health Research Unit, Barts and the London School of Medicine and Dentistry, Queen Mary University of London E1 2AB, UK.
• BMJ. 2016 Sep 6; 354: i4353.

ObjectiveTo determine the risks of stillbirth and neonatal complications by gestational age in uncomplicated monochorionic and dichorionic twin pregnancies.DesignSystematic review and meta-analysis.Data SourcesMedline, Embase, and Cochrane databases (until December 2015).Review MethodsDatabases were searched without language restrictions for studies of women with uncomplicated twin pregnancies that reported rates of stillbirth and neonatal outcomes at various gestational ages. Pregnancies with unclear chorionicity, monoamnionicity, and twin to twin transfusion syndrome were excluded. Meta-analyses of observational studies and cohorts nested within randomised studies were undertaken. Prospective risk of stillbirth was computed for each study at a given week of gestation and compared with the risk of neonatal death among deliveries in the same week. Gestational age specific differences in risk were estimated for stillbirths and neonatal deaths in monochorionic and dichorionic twin pregnancies after 34 weeks' gestation.Results32 studies (29 685 dichorionic, 5486 monochorionic pregnancies) were included. In dichorionic twin pregnancies beyond 34 weeks (15 studies, 17 830 pregnancies), the prospective weekly risk of stillbirths from expectant management and the risk of neonatal death from delivery were balanced at 37 weeks' gestation (risk difference 1.2/1000, 95% confidence interval -1.3 to 3.6; I(2)=0%). Delay in delivery by a week (to 38 weeks) led to an additional 8.8 perinatal deaths per 1000 pregnancies (95% confidence interval 3.6 to 14.0/1000; I(2)=0%) compared with the previous week. In monochorionic pregnancies beyond 34 weeks (13 studies, 2149 pregnancies), there was a trend towards an increase in stillbirths compared with neonatal deaths after 36 weeks, with an additional 2.5 per 1000 perinatal deaths, which was not significant (-12.4 to 17.4/1000; I(2)=0%). The rates of neonatal morbidity showed a consistent reduction with increasing gestational age in monochorionic and dichorionic pregnancies, and admission to the neonatal intensive care unit was the commonest neonatal complication. The actual risk of stillbirth near term might be higher than reported estimates because of the policy of planned delivery in twin pregnancies.ConclusionsTo minimise perinatal deaths, in uncomplicated dichorionic twin pregnancies delivery should be considered at 37 weeks' gestation; in monochorionic pregnancies delivery should be considered at 36 weeks.Systematic Review RegistrationPROSPERO CRD42014007538.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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