Neonatal Anthropometric Measurements: A Comparison of Neonates With 3-T Fetal MRI Exposure, With 1.5-T Fetal MRI Exposure, and Without In-Utero MRI Exposure.

Fetal MRI is increasingly performed at 3 T. Nonetheless, safety concerns persist regarding potential increased risk of intrauterine growth restriction from in-utero 3-T MRI exposure. The purpose of this study was to compare neonatal anthropometric measurements between neonates who underwent 3-T fetal MRI, neonates who underwent 1.5-T fetal MRI, and neonates without in-utero MRI exposure. This single-center retrospective study included gravid patients who underwent fetal ultrasound and possible 1.5-T or 3-T fetal MRI within 10 days between January 2017 and January 2022. For each included patient who also underwent 3-T fetal MRI, one matched patient who also underwent 1.5-T MRI and two matched patients without in-utero MRI exposure were randomly selected. Matching was based on gestational age at the time of the fetal ultrasound. Neonatal anthropometric characteristics were compared among groups. The final sample included 416 patients (mean age, 32 ± 5 [SD] years), 104 in the 3-T MRI group, 104 in the 1.5-T MRI group, and 208 in the MRI-unexposed group. The mean gestational age at the time of fetal ultrasound used for matching was 27 weeks 2 days in the 3-T group, 25 weeks 2 days in the 1.5-T group, and 26 weeks 0 days in the MRI-unexposed group ( = .07). The distribution of indications for fetal MRI was not significantly different between the 3-T and 1.5-T groups ( = .56). The mean gestational age at delivery was 37 weeks 5 days in the 3-T group, 38 weeks 0 days in the 1.5-T group, and 38 weeks 2 days in the unexposed group ( = .51). No significant difference was observed among the groups in mean neonatal weight (3 T: 3120 ± 753 [SD] g; 1.5 T: 3104 ± 704 g; unexposed: 2967 ± 614 g; = .09), mean neonatal weight percentile (3 T: 45 ± 27 [SD]; 1.5 T: 42 ± 26; unexposed: 41 ± 24; = .56), mean neonatal head circumference (3 T: 34 ± 3 [SD] cm; 1.5 T: 34 ± 3 cm; unexposed: 34 ± 2 cm; = .05), or mean neonatal head circumference percentile (3 T: 48 ± 29 [SD]; 1.5 T: 42 ± 23; unexposed: 43 ± 30; = .32). There were no significant differences in neonatal anthropometric measurements among neonates who underwent in-utero 3-T MRI, neonates who underwent in-utero 1.5-T MRI, and neonates without in-utero MRI exposure. The results support the safety of 3-T MRI with respect to the growth of the developing fetus.