Importance — Fetal safety of magnetic resonance imaging (MRI) in the first trimester of pregnancy, or with gadolinium enhancement at any time of pregnancy, is unknown.
Objective — To evaluate the long-term safety after exposure to MRI in the first trimester of pregnancy or to gadolinium at any time in pregnancy.
Design, Setting and Participants — Universal healthcare databases in the province of Ontario, Canada were used to identify all births > 20 weeks, from 2003-2015.
Exposure — MRI exposure in the first trimester of pregnancy, or gadolinium MRI exposure at any time in pregnancy.
Main Outcomes and Measures — For first-trimester MRI exposure, the risk of stillbirth or neonatal death < 28 days after birth, and any congenital anomaly, neoplasm, hearing loss or vision loss was evaluated from birth to age 4 years. For gadolinium-enhanced MRI in pregnancy, connective tissue or skin disease resembling nephrogenic systemic fibrosis (NSF-like), and a broader set of rheumatological, inflammatory or infiltrative skin conditions from birth, were identified.
Results — Of 1 424 105 deliveries, 48% were female, with a mean 39 weeks gestation. The overall rate of MRI was 3.97 per 1000. Comparing first-trimester MRI (n = 1737) to no MRI (n = 1 418 451), there were 19 and 9844 stillbirths/neonatal deaths, respectively (adjusted relative risk [aRR] 1.68, 95% CI 0.97-2.90) – an adjusted risk difference of 4.7 per 1000 (95% CI -1.6 to 11.0). The risk was also not significantly higher for congenital anomalies, neoplasm, vision loss or hearing loss. Comparing gadolinium-MRI (n = 397) to no MRI (n = 1 418 451), the hazard ratio for NSF-like outcomes was not statistically significant. The broader outcome of any rheumatological, inflammatory or infiltrative skin condition occurred in 123 vs. 384 180 births (aHR 1.36, 95% CI 1.09-1.69) – an adjusted risk difference of 45.3 per 1000 person-years (95% CI 11.3 to 86.8). Stillbirths/neonatal deaths occurred in 7 vs. 9844 pregnancies (aRR 3.70, 95% CI 1.55-8.85) – an adjusted risk difference of 47.5 per 1000 (95% CI 9.7-138.2).
Conclusions and Relevance — MRI exposure during the first trimester of pregnancy, compared with non-exposure, was not associated with increased risk for harm to the fetus or in early childhood. Gadolinium MRI at any time during pregnancy was associated with an increased risk for a broad set of rheumatological, inflammatory, or infiltrative skin conditions, and stillbirth/neonatal death. The study may not have been able to detect rare adverse outcomes.
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