Twin-to-twin transfusion syndrome: a model for the fetal origins of adult health.

Twin-to-twin transfusion syndrome (TTTS) is a complication of monochorionic, diamniotic twins that results from unbalanced blood flow from one to the other in utero. The increased rate of functional heart disease among the recipient twins in these pregnancies is a model for the theory of fetal origins of adult health. Potential mechanisms for heart disease include alterations in the hormonal environment within the fetal bodies, blood pressure-driven alterations in blood flow and blood vessel distensibility, abnormal differentiation of fetal myocardial cells and changes in coronary artery growth. Although there are no large studies showing adult consequences of this fetal physiological disturbance, paediatric problems certainly exist and predict an increased risk of adult disease.