Perinatal outcomes of twin births conceived using assisted reproduction technology: a population-based study†

(ART). Although many studies comparing ART and naturally conceived twins report no difference in risks for peri-natal outcomes, others report slight to moderate positive or protective associations. METHODS: We selected twin deliveries with and without indication of ART from Massachusetts live birth–infant death records from 1997 to 2000 linked to the US ART surveillance system. The sample was restricted to deliveries by mothers with increased socioeconomic status, private health insurance and intermediate/plus prenatal care use. Our final sample included 1446 and 2729 ART and non-ART twin deliveries, respectively. Odds ratios (OR) for associations between ART and perinatal outcomes were adjusted for maternal demographic factors, smoking, prenatal care and hospital care level. RESULTS: ART twin deliveries were less likely than non-ART to be very preterm (adjusted OR 0.75; 95 % con-fidence interval 0.58–0.97) or include a very low birthweight (<1500 g) infant (0.75; 0.58–0.95) or infant death (0.55; 0.35–0.88). In stratified analyses, these findings were observed among primiparous deliveries, but there were no risk differences among multiparous ART and non-ART twin deliveries. CONCLUSIONS: ART treatment was not a risk factor for adverse perinatal outcome, and risks for several outcomes were somewhat lower among ART twin deliv-eries. Nonetheless, ART is strongly associated with twinning and twins remain a high-risk group, relative to singletons