MR Imaging Measurements of Altered Placental Oxygenation in Pregnancies Complicated by Fetal Growth Restriction

Purpose: To evaluate oxygen-enhanced and blood oxygen level-dependent (BOLD) magnetic resonance (MR) imaging parameters in normal pregnancies and those complicated by fetal growth restriction (FGR). Materials and Methods: This case-control study was approved by the local research ethics committee. Informed consent was obtained from all subjects. From October 2010 to October 2015, 28 women with uncomplicated pregnancies (individualized birthweight ratio [IBR]> 20th percentile and delivery >37 weeks) and 23 with pregnancies complicated by FGR (IBR <5th percentile and abnormal Doppler ultrasonography [US] studies) underwent MR imaging. Differences in placental longitudinal R1 (1/T1) and transverse R2* (1/T2*) were quantified, with subjects breathing either air or oxygen. The difference in R1 (Delta R1) after hyperoxia was converted to change in partial pressure of oxygen (Delta Po-2). Data were acquired prospectively, with retrospective interpretation of group differences (unpaired t tests). Diagnostic models were developed by using logistic regression analysis with gestational age as a covariate. Results: The mean baseline R1 and R2* for normal pregnancies (R1: 0.59 sec(-1), 95% confidence interval [CI]: 0.58 sec(-1), 0.60 sec(-1); R2*: 17 sec(-1), 95% CI: 14 sec(-1), 20 sec(-1)) were significantly different from those of pregnancies complicated by FGR (R1: 0.63 sec(-1), 95% CI: 0.62 sec(-1), 0.65 sec(-1); R2*: 26 sec(-1), 95% CI: 22 sec(-1), 32 sec(-1)) (P <.0001). The Delta R1 showed a significant negative association with gestational age (P <.0001) in the combined cohort, with the FGR group having a Delta R1 that was generally 61.5% lower than that in the normal pregnancy group (P =.003). The area under the receiver operating characteristic curve for the differentiation between pregnancy complicated by FGR and normal pregnancy by using Delta Po-2, baseline R1, and baseline R2* was 0.91 (95% CI: 0.82, 0.99). Conclusion: R1, R2*, and Delta Po-2 were significantly different between normal pregnancies and those complicated by severe FGR. MR imaging parameters have the potential to help identify placental dysfunction associated with FGR and may have clinical utility in correctly identifying FGR among fetuses that are small for gestational age. A larger prospective study is needed to assess the incremental benefit beyond that offered by US. (C) RSNA, 2017