Magnetic resonance imaging measurement of placental perfusion and oxygen saturation in early-onset fetal growth restriction

Abstract

Objective: We hypothesised that a multi-compartment magnetic resonance imaging (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 ultrasound <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 was investigated, including the influence of GA at scan.

Results: The FGR group (mean GA 27⁺⁵ weeks, range 24⁺² to 33⁺⁶ weeks) had a significantly lower EFW compared with the control group (mean GA 29⁺¹ weeks; -705 g, 95% CI -353 to -1057 g). MRI-derived feto-placental oxygen saturation was higher in controls compared with FGR (75 ± 9.6% versus 56 ± 16.2%, P = 0.02, 95% CI 7.8-30.3%). Feto-placental oxygen saturation estimation correlated strongly with GA 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.

Tweetable abstract: MRI reveals differences in feto-placental oxygen saturation between normal and FGR pregnancy that is associated with disease severity.

Keywords: Fetal growth restriction; oxygenation; placenta; pregnancy; relaxometry.