Twins (6) Rates (6) Rates (5) Developed countries (4) monde (3) taux (3) Complications (3) Reproductive technology (3) Risk (3) Proportion (3) Paper (3) Mountains (3) Multiple birth (3) Sources (3) Sources (3) Women (3) Number (3) temps (durée) (2) risque (2) papier (2) carte (2) santé (2) comparaison (2) Comparison (2) Databases (2) Databases (2) Nineteen seventies (2) Databases (2) Women (2) Time (2)