MRI during first trimester does not pose risk to mother, fetus

Contrary to some conventional concerns, MRI scans in the first trimester of pregnancy appear safe for both mothers and their fetuses, according to a study published in the Journal of the American Medical Association. However, exposure to gadolinium of any kind, including in MRI, came with an increased risk of adverse effects to the child after birth.

The study authors speculate that this could be especially good news for physicians who are developing a “greater reliance on medical imaging,” and try to avoid imaging methods on pregnant women that include ionizing radiation, which MRI does not.

The researchers examined the health records of more than 1.42 million deliveries in Ontario, Canada, between 2003 and 2015. They examined the subsequent babies’ risk of stillbirth, death within 28 days of birth, congenital anomalies and certain bodily functions and potential diseases after being exposed to first-trimester MRI or gadolinium-enhanced MRI.

About 5,600 of the participating women had undergone an MRI during pregnancy—about 1,700 were in the first trimester and about 400 of them were gadolinium-enhanced (in any stage of pregnancy). When calculating the risk of such a procedure to the women’s children, the researchers had to take into account that the women who needed MRIs were more likely to have health problems (that necessitated MRIs) that could impact the health of their fetuses than the women who did not undergo MRIs at that time.

In the MRI-exposed group, there were 10.9 stillbirths or neonatal deaths per 1,000 births, while there were 6.9 such incidents per 1,000 in the non-exposed group. But the incidence of congenital anomalies was not much different between the two cohorts: 33.8 per 1,000 in the exposed women and 24 per 1,000 in the exposed women.

In the gadolinium-exposed cohort, there were 17.6 per 1,000 stillbirths or neonatal deaths. And the fetuses that had been exposed to gadolinium-enhanced MRI at any time during their mothers’ pregnancies grew up to be children with an increased incidence of rheumatological, inflammatory or infiltrative skin conditions: 125.8 per 1,000 people in the exposed cohort and 93.7 per 1,000 people in the non-exposed cohort. But the risk of congenital abnormalities between the two groups did not change.

The study authors were careful to point out that it’s possible there are other, rarer potential adverse effects of either type of MRI that were not captured in this study because of the relatively small cohort of women who received either procedure.

Still, it appears that regular MRI in the first trimester of pregnancy does not pose a statistically significant increase in risk to the fetus, while gadolinium exposure at any time during the pregnancy could be dangerous to the child. The researchers called for more investigation to determine the safety of non-gadolinium-enhanced MRI in the second and third trimester of pregnancy.