Association of placental T2 relaxation times and uterine artery Doppler ultrasound measures of placental blood flow

Purpose: To investigate whether, in the second trimester of pregnancy, placental T-2 relaxation time (determined using magnetic resonance imaging (MRI)) is related to impedance to flow in the uterine arteries. Methods: In 40 singleton pregnancies at 24-29 weeks' gestation, uterine artery pulsatility index (PI) was measured by Doppler ultrasound and T-2 relaxation time was measured by echo planar MRI at 1.5 T. The significance of the associations between T-2 relaxation time, uterine artery PI and birth weight were examined. Results: In 25 pregnancies that delivered small for gestational age (SGA) neonates with birth weight below the 10th percentile, compared to those with appropriate for gestational age (AGA) birth weight, the T-2 relaxation time was significantly decreased (88 ms vs. 149 ms, p < 0.0001) and uterine artery PI was increased (1.96 vs. 1.00, p < 0.0001). There were significant associations between placental T-2 relaxation time and log(10) uterine artery PI (r = -0.749, p < 0.0001), and between T-2 relaxation and birth weight percentile (r = 0.693, p < 0.0001). Conclusion: The T-2 relaxation time during the second trimester is shorter in pregnancies that subsequently deliver SGA neonates and the measurement is strongly correlated with impedance to flow in the uterine arteries. (C) 2013 Published by Elsevier Ltd.