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.

Abstract

<b>BACKGROUND.</b> 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. <b>OBJECTIVE.</b> 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. <b>METHODS.</b> 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. <b>RESULTS.</b> 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 (<i>p</i> = .07). The distribution of indications for fetal MRI was not significantly different between the 3-T and 1.5-T groups (<i>p</i> = .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 (<i>p</i> = .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; <i>p</i> = .09), mean neonatal weight percentile (3 T: 45 ± 27 [SD]; 1.5 T: 42 ± 26; unexposed: 41 ± 24; <i>p</i> = .56), mean neonatal head circumference (3 T: 34 ± 3 [SD] cm; 1.5 T: 34 ± 3 cm; unexposed: 34 ± 2 cm; <i>p</i> = .05), or mean neonatal head circumference percentile (3 T: 48 ± 29 [SD]; 1.5 T: 42 ± 23; unexposed: 43 ± 30; <i>p</i> = .32). <b>CONCLUSION.</b> 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. <b>CLINICAL IMPACT.</b> The results support the safety of 3-T MRI with respect to the growth of the developing fetus.