Fiona Cheong-See, clinical research fellow1, Ewoud Schuit, postdoctoral research fellow2 3 4, David Arroyo-Manzano, biostatistician5, Asma Khalil, consultant obstetrician6, Jon Barrett, senior scientist7, K S Joseph, professor of obstetrics and gynaecology8, Elizabeth Asztalos, associate professor9, Karien Hack, MD and PhD, in obstetrics and gynaecology10, Liesbeth Lewi, assistant professor in obstetrics and gynaecology11 12, Arianne Lim, gynaecologist13, Sophie Liem, MD in obstetrics and gynaecology13, Jane E Norman, professor of maternal and fetal health14, John Morrison, professor of obstetrics and gynaecology and paediatrics15, C Andrew Combs, associate director of research16, Thomas J Garite, director of research and education, professor emeritus of obstetrics and gynaecology16 17, Kimberly Maurel, associate director16, Vicente Serra, professor of obstetrics and gynaecology18 19, Alfredo Perales, professor of obstetrics and gynaecology19 20, Line Rode, senior resident21, Katharina Worda, specialist in obstetrics and gynaecology22, Anwar Nassar, professor of obstetrics and gynaecology23, Mona Aboulghar, professor of obstetrics and gynaecology24, Dwight Rouse, principal investigator, professor of obstetrics and gynaecology25, Elizabeth Thom, research professor of biostatistics and epidemiology26, Fionnuala Breathnach, consultant obstetrician and gynaecologist, senior lecturer in maternal fetal medicine26, Soichiro Nakayama, assistant professor27, Francesca Maria Russo, MD in obstetrics and gynaecology28, Julian N Robinson, chief of obstetrics and associate professor29, Jodie M Dodd, professor of obstetrics and gynaecology30, Roger B Newman, professor and Maas chair for reproductive sciences31, Sohinee Bhattacharya, senior lecturer32, Selphee Tang, data analyst33, Ben Willem J Mol, professor of obstetrics and gynaecology34, Javier Zamora, senior lecturer, head of clinical biostatistics unit, director of clinical epidemiology research area35 36, Basky Thilaganathan, professor and director of fetal medicine6, Shakila Thangaratinam, professor of maternal and perinatal health1, A Global Obstetrics Network (GONet) Collaboration

Abstract

Objective To determine the risks of stillbirth and neonatal complications by gestational age in uncomplicated monochorionic and dichorionic twin pregnancies.

Design Systematic review and meta-analysis.

Data sources Medline, Embase, and Cochrane databases (until December 2015).

Review methods Databases 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.

Results 32 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; I2=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; I2=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; I2=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.

Conclusions To 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 registration PROSPERO CRD42014007538.

BMJ