ObjectiveThis study aimed to explore the impacts of the changing national fertility policy on maternal and fetal characteristics, and birth timing patterns and provide a basis for the management of the obstetric and midwifery workforce.DesignRetrospective cohort study.SettingData from medical register of a tertiary referral centre in Beijing, China.ParticipantsWe included 20 334 births with a gestational age more than 28 weeks during January 2013–September 2023.Main outcomesThe main outcomes included birth numbers, maternal age, parity, birth modes, premature rates, neonatal birth weight, and birth timings.ResultsThe birth rates showed a general rising trend before 2016. Afterwards, the birth rates kept decreasing and reached the bottom level in 2022. The caesarean section rates showed a declining trend, while the assisted birth rates were progressively rising, especially among primiparous women. From 2013 to 2022, the proportions of multiparous women (increasing from 9.3% to 36.6%) and women with advanced maternal age (increasing from 11.4% to 34.5%) were on the rise, together with increasing rates of premature birth (increasing from 5.7% to 8.5%) and neonatal low birth weight (rising from 4.3% to 7.2%) in this population. This study found a significant peak of births between 14:00 and 15:00, which remained unchanged despite shifts in the fertility policy (p<0.001 andR¯values close to 1, respectively).ConclusionThe ‘three-child’ policy did not boost the birth rate further 2 years later after its enactment, and the proportion of multiparous women and women with advanced maternal age were on the rise, accompanied by an increase in rates of premature birth and low birth weight. Targeted training should be offered to healthcare professionals to empower them to deal with possible negative pregnancy outcomes and childbirth complications. Prepregnancy and antepartum education should be parity specific. Adequate midwifery staffing during this 14:00–15:00 is vital to promote a safe birth.