The addition of in-utero MRI (iuMRI) to the arsenal of imaging modalities for detecting fetal brain anomalies often leads to changes in patient management due to improved diagnostic accuracy and confidence, according to results from the MERIDIAN study.1
Approximately 1 in 1000 pregnancies are complicated by fetal brain abnormalities, the primary mode of detection for which is fetal ultrasonography. However, there is limited evidence for the use of iuMRI to aid in the detection of these abnormalities. Professor Paul D. Griffiths, PhD, FRCR, of the University of Sheffield, United Kingdom, and colleagues sought to clarify the diagnostic accuracy and clinical impact of iuMRI in detecting fetal brain abnormalities in the MERIDIAN study. The results were published in The Lancet.
The investigators conducted a multicenter prospective cohort study in 16 fetal medical centers in the United Kingdom. The study included pregnant women 16 years of age and older whose fetuses were initially found to have a fetal brain abnormality on ultrasound. Other inclusion criteria included gestational age of 18 weeks and older and no contraindications for MRI. Accuracy was estimated after the findings were reviewed by 2 independent panels.
Outcome reference diagnoses were obtained in 638 fetuses that underwent iuMRI, 570 of which had iuMRI within 2 weeks of ultrasonography. The 570 fetuses were divided into 2 cohorts: 18 to ˂24 weeks’ gestation (n = 369) and ≥24 weeks’ gestation (n = 201).
Overall, ultrasonography had a diagnostic accuracy of 68% compared with 93% with iuMRI (95% CI, 21-29; P <.0001). Ultrasonography had reduced diagnostic accuracy in fetuses older than 24 weeks (64%) compared with fetuses at 18 to 24 weeks’ gestation (70%); there was little difference in diagnostic accuracy between gestational ages with iuMRI (94% and 92%). Of note, incorrect ultrasonography reports were corrected by iuMRI in 25% of cases.
The investigators also noted that iuMRI contributed additional diagnostic information in 49% of the participants, with a documented change in prognosis or major effects on counseling in 44% and 15% of cases, respectively.
The decreased diagnostic accuracy of fetal ultrasonography after 24 weeks is thought to be related to the position of the fetal head in the maternal pelvis, the increased size of the mother, and ossification of the fetal skull, suggesting that “iuMRI significantly increases the accuracy of fetal brain diagnoses compared to ultrasound alone in all fetuses 18 weeks and older.”
Further, the investigators pointed out that compared with ultrasonography, iuMRI allowed more cases to be categorized as “normal,” “favorable,” or “poor” compared with “intermediate” or “unknown,” which has a significant effect on decision making, especially in cases where termination of pregnancy was indicated.
The researchers concluded that, “The increased diagnostic accuracy and confidence [of iuMRI] results in changes in counselling and clinical management in a high proportion of cases.”
Griffiths PD, Bradburn M, Campbell MJ, et al. Use of MRI in the diagnosis of fetal brain abnormalities in utero (MERIDIAN): a multicentre, prospective cohort study. Lancet. 2017;389:538-546. doi: 10.1016/S0140-6736(16)31723-8