Natural versus induced twinning and pregnancy outcome: a Dutch nationwide survey of primiparous dizygotic twin deliveries.

OBJECTIVE: To compare obstetrical outcome of twin pregnancies after assisted reproduction with that of natural twin pregnancies.

DESIGN: Retrospective national database study.

SETTING: Academic Medical Centre.

PATIENT(S): One thousand ninety-three primiparous mothers registered in the Dutch National Birth Registry who gave birth to a dizygotic (DZ) twin (male/female) in 1994, 1995, and 1996. We compared 613 natural twin pregnancies and 480 twin pregnancies born after assisted reproduction.

MAIN OUTCOME MEASURE(S): Gestational length, mode of delivery, mode of presentation of the children, birth weight, APGAR score, congenital anomalies, perinatal mortality rate, highest recorded maternal diastolic blood pressure, and maternal postpartum complications.

RESULT(S): Rates of perinatal mortality and very premature parturition (<29 weeks) were lower in natural twin mothers. Overall, induced DZ twins were born 3.5 days earlier with a lower birth weight and APGAR score compared with controls. Rates of congenital anomalies and incidence of cesarean section were not different. The highest recorded diastolic blood pressure was lower in induced twinning with a 30% lower incidence of diastolic blood pressure >90 mm Hg.

CONCLUSION(S): Obstetric outcome for induced DZ twin pregnancy is less optimal than in natural DZ twin pregnancy. Twinning in assisted reproduction is known for its contribution to the high rate of premature deliveries, but in addition being a subfertile patient undergoing treatment makes an intrinsic contribution to adverse events as well.