MRI Measurement of Placental Perfusion and Oxygen Saturation in Early Onset Fetal Growth Restriction.

OBJECTIVE We hypothesized that a multi-compartment MRI technique that is sensitive to fetal blood oxygenation would identify changes in placental blood volume and fetal blood oxygenation in pregnancies complicated by early-onset Fetal Growth Restriction (FGR). DESIGN Case-Control study. SETTING London, UK. POPULATION Women with uncomplicated pregnancies (estimated fetal weight, EFW>10th centile for gestational age, GA and normal maternal and fetal Doppler ultrasound, n=12) or early-onset FGR (EFW<3rd centile with or without abnormal Doppler US<32 weeks GA, n=12) were studied. METHODS All women underwent MRI examination. Using a multi-compartment MRI technique, we quantified fetal and maternal blood volume and feto-placental blood oxygenation. MAIN OUTCOME MEASURES Disease severity was stratified according to Doppler pulsatility index and the relationship to the MRI parameters investigated, including the influence of gestational age at scan. RESULTS The FGR group (mean GA:27+5wks, range:24+2 to 33+6wks) had a significantly lower estimated fetal weight compared to the control group (mean GA:29+1wks) (-705g 95%CI=(-353, -1057g)). MR-derived feto-placental oxygen saturation was higher in controls compared to FGR (75 (±9.6)% vs 56 (±16.2)%, p=0.02, 95%CI=(7.8-30.3)%). Feto-placental oxygen saturation estimation correlated strongly with gestational age at scan in controls (r=-0.83) CONCLUSION: Using a novel multimodal MRI protocol we demonstrated reduced feto-placental blood oxygen saturation in pregnancies complicated by early-onset FGR. The degree of abnormality correlated with disease severity defined by ultrasound Doppler findings. Gestational age dependent changes in oxygen saturation were also present in normal pregnancies.