In vivo MRI assessment of placental and foetal oxygenation changes in a rat model of growth restriction using blood oxygen level-dependent (BOLD) magnetic resonance imaging.

OBJECTIVES

To evaluate whether changes in BOLD signal intensities following hyperoxygenation are related to intrauterine growth restriction (IUGR) in a rat model.

METHODS

IUGR was induced in pregnant rats by ligating the left vascular uterine pedicle at day 16 of gestation. BOLD MR imaging using a balanced steady-state free-precession (balanced-SSFP) sequence on a 1.5-T system was performed on day 19. Signal intensities (SI) before and after maternal hyperoxygenation were compared in the maternal liver and in control and growth-restricted foetoplacental units (FPUs).

RESULTS

Maternal hyperoxygenation resulted in a significant increase in SI in all regions of interest (P < 0.05) in the 18 rats. In the control group, the SI (mean ± SD) increased by 21 % ± 15 in placentas (n = 74) and 13 % ± 8.5 in foetuses (n = 53). In the IUGR group, the increase was significantly lower: 6.5 % ± 4 in placentas (n = 36) and 7 %± 5.5 in foetuses (n = 34) (P < 0.05).

CONCLUSION

BOLD MRI allows non-invasive assessment of the foetoplacental response to maternal hyperoxygenation in the rat and demonstrates its alteration in an IUGR model. This imaging method may provide a useful adjunct for the early diagnosis, evaluation, and management of human IUGR.

KEY POINTS: • Intra-uterine growth restriction is an important cause of perinatal morbidity and mortality. • Blood oxygen level-dependent MRI non-invasively assesses foetoplacental response to maternal hyperoxygenation. • In the rat, foetoplacental response to maternal hyperoxygenation is altered in IUGR. • Functional MRI may help to assess human IUGR.