Lower risks of adverse outcome in twins conceived by artificial reproductive techniques compared with spontaneously conceived twins

The outcomes of twins conceived by 136 women after medical assistance (MA)such as ovulation induction with or without assisted reproductivetechniques, and twins conceived spontaneously (SP) by 72 women werecompared. All 208 women were monitored from < 20 weeks gestation; theyall delivered at > or = 24 weeks gestation. The chorionicity of theplacenta was diagnosed antenatally and confirmed after delivery. There were10 perinatal deaths; the physical and neurological status of the remaining406 infants was assessed at 1 year of corrected age. There were nodifferences in gestational age at birth, the birth weights of the largerand smaller twins, the birth weight discordance, or the incidence oflife-threatening major malformations between groups. Adverse infantoutcomes, such as death, cerebral palsy and mental retardation occurred innine (3.3%) of 272 MA twins compared with 12 (8.3%) of 144 SP twins (P <0.05). The placenta was monochorionic in only three (2.2%) of 136 MA twinpregnancies compared with 41 (57%) of 72 SP twin pregnancies (P <0.001). Of the 21 infants with adverse outcomes, nine had monochorionicplacentas. Thus, the risk of an adverse outcome was 2.8-fold higher (95%confidence interval (CI) 1.2- 6.4) in monochorionic twins than indichorionic twins (10 versus 3.7%; P < 0.05). There was no difference inthe incidence of adverse infant outcomes between SP (4.8%) and MA (3.4%)twins with dichorionic placentas. These findings suggest that ovulationinduction in itself was not associated with an adverse outcome of twinpregnancies. The lower frequency of monochorionic placentas in MA twins mayhave been responsible for the lower risk of an adverse outcome in MA twins.