This observational data collection study will include subjects with ultrasound-confirmed twin pregnancy and planned NIPS zygosity assessment as a part of their clinical care. Initial chorionicity assessment and, when available, planned twin pregnancy management (e.g., frequency of prenatal ultrasounds, maternal fetal medicine (MFM) referral etc) will be recorded in the study database. Following zygosity results being returned through clinical care NIPS, updated chorionicity \& amnionicity will again be recorded in the study database. Other clinical data in the medical record as part of clinical care, including monochorionic twin pregnancy complications (TTTS, FTC referral, etc), placenta pathology findings, and delivery and neonatal outcomes will also be recorded in the study database. There will be no study blood sample collection or other study procedures performed as part of this study.
