MRI use in the first trimester of pregnancy is not harmful to the fetus, although gadolinium-enhanced MRI use at any point during pregnancy is associated with rare adverse outcomes in childhood, according to a study published in JAMA.
Investigators sought to identify all births of more than 20 weeks between 2003 and 2015 in Ontario, Canada, in which MRI exposure in the first trimester of pregnancy or gadolinium MRI exposure at any time in pregnancy was used. For first-trimester MRI exposure, the researchers evaluated the risk of stillbirth or neonatal death within 28 days of birth and any congenital anomaly, neoplasm, and hearing or vision loss from birth to age 4 years. For gadolinium-enhanced MRI in pregnancy, they identified connective tissue or skin disease resembling nephrogenic systemic fibrosis (NSF-like) and rheumatologic, inflammatory, or infiltrative skin conditions from birth.
Among 1,424,105 deliveries (48% girls; mean gestational age, 39 weeks), the overall rate of MRI use was 3.97 per 1,000 pregnancies. In a comparison of first-trimester MRI use (n=1,737) with no use of MRI (n=1,418,451), 19 stillbirths or deaths occurred vs 9,844 in the unexposed group (adjusted relative risk [RR], 1.68), for an adjusted risk difference of 4.7 per 1,000 person-years. According to the investigators, the risk was also not significantly higher for congenital anomalies, neoplasm, or vision or hearing loss.
In a comparison of gadolinium MRI (n=397) with no use of MRI (n=1,418,451), the researchers found that the hazard ratio for NSF-like outcomes was not statistically significant. In addition, the broad outcome of any rheumatologic, inflammatory, or infiltrative skin condition was higher after use of gadolinium MRI (125.8 per 1,000 person-years [123 events]) than with no MRI use (93.7 per 1,000 person-years [384,180 events]), with an adjusted HR of 1.36 and an adjusted risk difference of 45.3. Stillbirths and neonatal deaths occurred in 7 MRI-exposed pregnancies vs 9,844 unexposed pregnancies (adjusted RR, 3.70), for an adjusted risk difference of 47.5 per 1,000 pregnancies.
“Pregnancy is not a contraindication to MRI, which provides highly detailed images without the use of ionizing radiation,” stated Joel G. Ray, MD, MSc, FRCPC, from the Departments of Medicine, and Obstetrics and Gynecology, St Michael’s Hospital, Toronto, and colleagues. “We did not evaluate the safety of MRI after the first trimester, as some nongadolinium MRIs are performed in the second or third trimester for a fetal indication, such as a fetal anomaly or tumor, heightening the chances of confounding by indication.
“Following inadvertent or prior to intentional MRI exposure in the first trimester, a discussion about a potentially slightly higher risk of vision loss in the child should be balanced by an acknowledgment that it is not known to be associated with a higher risk of other adverse outcomes,” the researchers continued. “Since tissue energy deposition generally increases with field strength and, for most indications, standard 1.5-T MRI scanners generates quality diagnostic images, it seems prudent to avoid more than 1.5-T MRI for pregnant women. Until further studies are done, these findings suggest that gadolinium contrast should be avoided during pregnancy.”
- Ray JG, Vermeulen MJ, Bharatha A, et al. Association between MRI exposure during pregnancy and fetal and childhood outcomes. JAMA. 2016;316(9):952-961. doi:10.1001/jama.2016.12126.