OBJECTIVE: To compare the effect of maternal age on assisted reproductive technology (ART) and spontaneous conception (SC) pregnancies regarding maternal and neonatal complications.

DESIGN: Nordic retrospective population-based cohort study. Data from national ART registries were cross-linked with national medical birth registries.

SETTING: Not applicable.

PATIENT(S): A total of 300,085 singleton deliveries: 39,919 after ART and 260,166 after SC.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): Hypertensive disorders in pregnancy (HDP), placenta previa, cesarean delivery, preterm birth (PTB; <37 weeks), low birth weight (LBW; <2,500 g), small for gestational age (SGA), and perinatal mortality (≥28 weeks). Adjusted odds ratios (AORs) were calculated. Associations between maternal age and outcomes were analyzed.

RESULT(S): The risk of placenta previa (AOR 4.11-6.05), cesarean delivery (AOR 1.18-1.50), PTB (AOR 1.23-2.19), and LBW (AOR 1.44-2.35) was significantly higher in ART than in SC pregnancies for most maternal ages. In both ART and SC pregnancies, the risk of HDP, placenta previa, cesarean delivery, PTB, LBW, and SGA changed significantly with age. The AORs for adverse neonatal outcomes at advanced maternal age (>35 years) showed a greater increase in SC than in ART. The change in risk with age did not differ between ART and SC for maternal outcomes at advanced maternal age.

CONCLUSION(S): Having singleton conceptions after ART results in higher maternal and neonatal outcome risks overall, but the impact of age seems to be more pronounced in couples conceiving spontaneously.