Impact of implementation of twin-specific growth charts on adverse perinatal outcomes in twin pregnancies: an interrupted time series analysis

OBJECTIVE: Twin pregnancies are associated with higher perinatal mortality and morbidity. The assessment of fetal growth in these pregnancies using singleton or twin charts remains controversial. The aim of this study was to evaluate the impact of the implementation of twin-specific growth charts on adverse perinatal outcomes in twin pregnancies. METHODS: weeks), iatrogenic preterm birth, stillbirth, and neonatal unit admission. Interrupted time series (ITS) analysis with segmented regression of semiannual data assessed immediate and trend changes following implementation. RESULTS: 2008 twin pregnancies were analysed, including 1533 in the pre-intervention and 475 in the post-intervention period. Following implementation, the rates of SGA and FGR diagnoses per fetus decreased substantially (SGA: 53.2% vs. 11.0%; FGR: 47.1% vs. 6.8%; both p < 0.001). ITS analysis demonstrated immediate reductions in FGR (-40.0%, p < 0.001) and SGA (-42.8%, p < 0.001) diagnoses following the policy change, with no significant change in trend. Iatrogenic preterm birth showed a significant immediate reduction (-13.6%, p = 0.016), although without a sustained trend. No intervention effects were identified for stillbirth or neonatal unit admission rates (p > 0.05 for both). CONCLUSION: Use of twin-specific charts for antenatal growth surveillance was associated with fewer diagnoses of SGA and FGR and an immediate, but not sustained, reduction in iatrogenic preterm birth. No worsening was observed in the adverse perinatal outcomes assessed, including stillbirth and neonatal unit admission.