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Third-trimester ultrasound is highly predictive of how the first twin will present at birth. In a cohort of 238 twin pregnancies, ultrasound after 28 weeks correctly forecast cephalic presentation 95 % of the time, and after 32 weeks it predicted both cephalic and noncephalic presentations in >90 % of cases [Schwartz, 2012, 22680064]. Similar longitudinal data show that 96 % of twins keep the same presentation between 32–35 weeks and delivery, making vertex presentation especially stable [Park, 2018, 29792247].