MRI measurements for normal fetal aortic arch isthmus diameter and ductus arteriosus diameter between 20 to 36 gestational weeks / 中华围产医学杂志

ABSTRACT

Objective:To investigate the feasibility of MRI measurement for normal fetal aortic arch isthmus diameter and ductus arteriosus diameter between 20 to 36 weeks of gestation and analyze its relationship with gestational age.Methods:This retrospective study enrolled 257 pregnant women with an unclear fetal four-chamber view in prenatal ultrasonography, whose following fetal MRI examination results showed no structural cardiac abnormalities, in Shanghai Children's Medical Center Affiliated to the Medical College of Shanghai Jiaotong University from June 2018 to June 2020. Postnatal echocardiography confirmed cardiac structures were normal in all cases. MRI images were reviewed to measure the diameter of the aortic arch isthmus, defined as the aortic arch isthmus's central diameter, in the transverse section of the aortic arch in steady-state free precession sequence imaging and the diameter of ductus arteriosus near the descending aorta. The average values were calculated after repeating each measurement three times. The 5th, 50th and 95th percentiles and their 95% CI of the aortic arch isthmus diameter and the ductus arteriosus diameter corresponding to different gestational age and the mean value and its 95% CI of the ratio of the aortic arch isthmus diameter to the ductus arteriosus diameter were calculated. Pearson correlation analysis and regression analysis were used to evaluate the relationship of the aortic arch isthmus diameter and the ductus arteriosus diameter with gestational age. Results:The regression equation between the aortic arch isthmus diameter and gestational age was as follows the aortic arch isthmus diameter (mm) =-2.85+0.22×gestational age (weeks), and there was a positive linear correlation between them ( R2=0.737, P<0.001). The 50th percentile of the aortic arch isthmus diameter was 1.8-3.5 mm at 20-28 weeks and 3.5-5.0 mm at 28-36 weeks. The regression equation between the diameter of ductus arteriosus and gestational age was as follows the diameter of ductus arteriosus (mm) =-2.17+0.19×gestational age (weeks), and a positive linear correlation between them was revealed ( R2=0.606, P<0.001). The 50th percentile of the diameter of ductus arteriosus was 2.0-3.5 mm at 20-28 weeks and 3.2-4.8 mm at 28-36 weeks. The 95% CI for the ratios of the aortic arch isthmus diameter to the ductus arteriosus diameter at 20, 22, 24, 26, 28, 30, 32, 34 and 36 weeks of gestation were 0.8-1.1, 0.8-1.0, 0.8-1.0, 0.8-1.3, 0.8-1.5, 0.9-1.5, 0.9-1.7, 0.9-1.1 and 1.0-1.3, respectively, and were all close to 1. Conclusions:It is feasible to measure fetal aortic arch isthmus diameter and ductus arteriosus diameter at 20-36 weeks of gestation in MRI, and both measurements have a linear correlation with gestational age.