Objectives To determine whether integrated maternity care is associated with reduced preterm births (PTB) and fewer small-for-gestational-age infants (SGA), and whether its implementation leads to a reduction of secondary care consultations.Design Retrospective study.Setting Integrated maternity care organisation in the southwestern region of the Netherlands.Participants All singleton pregnancies (≥24 weeks) within integrated maternity care organisation Annature between 2015 and 2020.Intervention Implementation of a shared maternity record in primary and secondary care.Methods Data of 20 818 women were derived from patient records and from the Netherlands Perinatal Registry. Intervention was the introduction of integrated maternity care in January 2018. Through multivariate logistic regression and segmented regression analysis we assessed the combined prevalence of SGA and PTB (SGA-PTB) before (2015–2017), and after the intervention (2018–2020). Regional rates were contrasted with nationwide rates (n=782 176).Main outcome measures SGA-PTB prevalence and mean number of secondary care consultations per pregnancy.Results SGA-PTB prevalence declined from 618/3443 (17.9%) in 2015 to 560/3501 (16.0%) in 2017 to 507/3459 (14.7%) in 2020 (p<0.005). Mean number of secondary care consultations declined from six per pregnancy in 2015 to three in 2020. Logistic regression demonstrated a significant decline in odds of SGA-PTB (OR 0.83 (95% CI 0.77 to 0.89)) between 2015–2017 and 2018–2020 adjusted for changes in sociodemographic characteristics over time. A statistically significant average monthly 7.3% (p=0.05) reduction in SGA-PTB prevalence and 12.4% (p<0.005) mean monthly reduction in secondary care consultations were demonstrated for 2015–2017. Immediately after the intervention, mean monthly prevalence of SGA-PTB dropped non-significantly to 14.7%. Between 2018 and 2020 a significant 15.2% (p<0.005) reduction in secondary care consultations was shown.Conclusion Our results suggest that implementation of ...