Objectives The aim of this study is to compare the early perinatal loss rates between MC and dichorionic (DC) twins in an era of invasive treatment for TTTS.

Methods This was a retrospective study of all twin pregnancies of known chorionicity from a large regional cohort of 9 hospitals over a ten year period. Ultrasound data were matched to hospital delivery records and a mandatory national register of pregnancy losses. Prospective risk of pregnancy loss from 14 to 24 weeks’ gestation was calculated and the survival trend of MC and DC twins was analysed using Kaplan-Meier survival analysis.

Results The analysis included 3117 twin pregnancies (605 MC and 2512 DC). The total risk of early pregnancy loss (miscarriage and neonatal death) before 24 weeks in MC twins (60.3 per 1000 fetuses) was significantly higher than in DC twins (6.5 per 1000 fetuses), with a hazard ratio (HR) of 9.18 (95% CI, 6.0–13.9). Survival analysis showed a significant difference in overall and early mortality between MC and DC twins (Log-rank test, p < 0.0001), while no difference was noted after 24 weeks of gestation (Log-rank test, p = 0.08).

Conclusions Early pregnancy loss is significantly more common in MC than in DC twins, but the trend in prospective risk of mortality in MC twins is not evident after 24 weeks’ gestation. This rate has almost halved compared to those in the published literature. Early detection and prompt treatment of complications in MC twins is likely to have contributed to this improvement in outcomes.