TRAP Intervention STudy: Early Versus Late Intervention for Twin Reversed Arterial Perfusion Sequence

Inclusion Criteria: * TRAP sequence in a monochorionic diamniotic twin pregnancy diagnosed between 11.6 and 13.6 weeks, as determined by the crown-rump length of the pump twin in spontaneous conceptions and by the date of insemination or embryonic age at replacement in pregnancies resulting from subfertility treatment * Women aged 18 years or more, who are able to consent * Anatomically normal pump twin * Provide written informed consent to participate in this randomized controlled trial, forms being approved by the Ethical Committees Exclusion Criteria: * Contraindication for an intervention due to a severe maternal medical condition or threatening miscarriage * Inaccessibility of the acardiac twin due to a retroverted uterus, severe maternal obesity, uterine fibroids, bowel or placental superposition * A major anomaly in the pump twin, requiring surgery or leading to infant death or severe handicap * Spontaneous arrest of the reverse flow and/or pump twin demise at diagnosis