Twin Pregnancy Monitoring: Chorionicity, TTTS and Scan Schedule
Twin pregnancy monitoring depends on chorionicity, meaning whether the twins share a placenta. This is best determined by ultrasound at 11–14 weeks. Twins with separate placentas (DCDA) usually have scans every four weeks from 20 weeks, while twins sharing a placenta (MCDA) need scans every two weeks from 16 weeks to detect twin-to-twin transfusion syndrome (TTTS) early.