Objective To document longitudinal changes in brain development in fetuses with congenital diaphragmatic hernia (CDH). Design Retrospective cohort study Setting Single tertiary fetal surgery center Population Fetuses with isolated CDH and at least two MRI-examinations (n=42 fetuses). Fifty-six fetuses who underwent MRI for a condition not interfering with fetal brain development or fetuses from healthy volunteers served as controls. Methods Biometry included biparietal and fronto-occipital diameter, ventricular atrial width, transcerebellar diameter, head circumference and width of the extra-axial space. Cortical maturation was assessed using a qualitative and quantitative grading system. 3D volumes were segmented for white matter, intra-axial and extra-axial cerebrospinal fluid and cerebellum. Main outcome measures Brain development on MRI with subjective and objective assessment. Results The mean GA at first MRI was 28.0 ± 2.1 wks and at the second 33.2 ± 1.3 wks. The mean GA in controls was 30.7 ± 4.2 wks. At 28 weeks CDH fetuses displayed abnormal maturation grading (p<0.003) and fissure depth (p<0.05). By 33 wks, the brain grading indices were still abnormal (p<0.01), but fissure depth measurements were in the normal range (p>0.05). Also, the extra-axial fluid and the ventricular volume were increased (resp. p 0.0054 and p 0.0243). There was no difference in white matter or cerebellum volume (p>0.05). Conclusions Brain development in CDH fetuses around 28 weeks appears to be delayed. This is less prominent at 33 weeks. In addition, there was an increase in ventricular and extra-axial space volume in the third trimester.