Longitudinal Trajectories of Regional Cerebral Blood Flow in Very Preterm Infants during Third Trimester ex Utero Development Assessed with MRI

Background: The third trimester of gestation is a crucial phase of rapid brain development, but little has been reported on the trajectories of cerebral blood flow (CBF) in preterm infants in this period. Purpose: To quantify regional CBF in very preterm infants longitudinally across the ex utero third trimester and to determine its relationship with clinical factors associated with brain injury and premature birth. Materials and Methods: In this prospective study, very preterm infants were enrolled for three longitudinal MRI scans, and 22 healthy full-term infants were enrolled for one term MRI scan between November 2016 and February 2019. Global and regional CBF in the cortical gray matter, white matter, deep gray matter, and cerebellum were measured using arterial spin labeling with postlabeling delay of 2025 msec at 1.5 T and 3.0 T. Brain injury and clinical risk factors in preterm infants were investigated to determine associations with CBF. Generalized estimating equations were used to account for correlations between repeated measures in the same individual. Results: A total of 75 preterm infants (mean postmenstrual age [PMA]: 29.5 weeks +/- 2.3 [standard deviation], 34.9 weeks +/- 0.8, and 39.3 weeks +/- 2.0 for each scan; 43 male infants) and 22 full-term infants (mean PMA, 42.1 weeks +/- 2.0; 13 male infants) were evaluated. In preterm infants, global CBF was 11.9 mL/100 g/min +/- 0.2 (standard error). All regional CBF increased significantly with advancing PMA (P <= .02); the cerebellum demonstrated the most rapid CBF increase and the highest mean CBF. Lower CBF was associated with intraventricular hemorrhage in all regions (P <= .05) and with medically managed patent ductus arteriosus in the white matter and deep gray matter (P = .03). Mean CBF of preterm infants at term-equivalent age was significantly higher compared with full-term infants (P <= .02). Conclusion: Regional cerebral blood flow increased significantly in preterm infants developing in an extrauterine environment across the third trimester and was associated with intraventricular hemorrhage and patent ductus arteriosus. (C) RSNA, 2021