To investigate the effect of the Assisted Reproduction Act, implemented in 2007 in Taiwan to reduce the number of embryos to transfer, on the trends over time regarding the rate of multiple births, preterm delivery, low birth weight (LBW), and small for gestational age (SGA) among deliveries using assisted reproductive technology (ART).

From the Birth Reporting Registry and the Assisted Reproduction Registry, we retrieved data of 4 016 530 live birth deliveries between 2001 and 2020; among them 71 000 (1.77%) were after ART. We calculated the rate of multiples and perinatal outcomes per 1000 deliveries annually from 2001 to 2020 for deliveries using and not using ART and computed the population attributable risk. We performed interrupted time series to assess the effect of the intervention, ie, the Assisted Reproduction Act.

The proportion of deliveries following ART was 0.57% in 2001 and increased to 4.03% in 2020. After the intervention, there were decreasing trends over time for rates of multiples (−10.63 per year, P < .001), preterm delivery (−6.74, P = .003), LBW (−9.38, P < .001), and SGA (−4.48, P = .001) among ART deliveries. There was also an immediate decrease right after intervention (−53.45, P = .005) for SGA after ART. The population attributable risk trends before and after intervention were both increasing for all outcomes.

The Assisted Reproduction Act in Taiwan was associated with a decreasing trend of multiples, preterm delivery, LBW, and SGA over time since 2008 among ART deliveries. In particular, there was an immediate decrease of SGA right after the intervention.