Objectives The COVID-19 pandemic and associated lockdowns disrupted health care worldwide. High-income countries observed a decrease in preterm births during lockdowns, but maternal pregnancy–related outcomes were also likely affected. This study investigates the effect of the first COVID-19 lockdown (March–June 2020) on provision of maternity care and maternal pregnancy–related outcomes in the Netherlands. Study design National quasi-experimental study. Methods Multiple linked national registries were used, and all births from a gestational age of 24+0 weeks in 2010–2020 were included. In births starting in midwife-led primary care, we assessed the effect of lockdown on provision of care. In the general pregnant population, the impact on characteristics of labour and maternal morbidity was assessed. A difference-in-regression-discontinuity design was used to derive causal estimates for the year 2020. Results A total of 1,039,728 births were included. During the lockdown, births to women who started labour in midwife-led primary care (49%) more often ended at home (27% pre-lockdown, +10% [95% confidence interval: +7%, +13%]). A small decrease was seen in referrals towards obstetrician-led care during labour (46%, −3% [−5%,−0%]). In the overall group, no significant change was seen in induction of labour (27%, +1% [−1%, +3%]). We found no significant changes in the incidence of emergency caesarean section (9%, −1% [−2%, +0%]), obstetric anal sphincter injury (2%, +0% [−0%, +1%]), episiotomy (21%, −0% [−2%, +1%]), or post-partum haemorrhage: >1000 ml (6%, −0% [−1%, +1%]). Conclusions During the first COVID-19 lockdown in the Netherlands, a substantial increase in homebirths was seen. There was no evidence for changed available maternal outcomes, suggesting that a maternity care system with a strong midwife-led primary care system may flexibly and safely adapt to external disruptions.