R1 and R2* changes in the human placenta in response to maternal oxygen challenge

Purpose Pregnancy complications such as preeclampsia and fetal growth restriction are sometimes thought to be caused by placental abnormalities associated with reduced oxygenation. Oxygen-enhanced MRI (R1 contrast) and BOLD MRI (R2* contrast) have the potential to noninvasively investigate this oxygen environment at a range of gestational ages. Methods Scanning was carried out at 1.5 T under maternal air and oxygen breathing in a single placental slice in 14 healthy pregnant subjects of gestational ages 21-37 weeks. We report R1 changes using a respiratory-triggered inversion recovery-turbo spin-echo sequence, which is sensitive to changes in PO2, and R2* changes using a breathhold multiple gradient-recalled echo sequence sensitive to changes in oxygen saturation. Results Significant R1 increases (P <0.005, paired t-test) and R2* decreases (P <0.0001, paired t-test) between air and oxygen breathing were demonstrated. ΔR1 decreased with gestational age (P <0.0005, r = -0.835, Pearson correlation test). No significant effect of gestational age on R2* change was observed. Conclusion The results demonstrate the feasibility of non-invasive investigation of placental oxygenation using MRI and the sensitivity of R 1 oxygen-enhanced MRI to gestational age. The techniques have the potential to provide unique noninvasive biomarkers in compromised pregnancies. Magn Reson Med 70:1427-1433, 2013. © 2012 Wiley Periodicals, Inc. Copyright © 2012 Wiley Periodicals, Inc.