Placental baseline conditions modulate the hyperoxic BOLD-MRI response

Area of Science:

• Obstetrics and Gynecology
• Radiology
• Fetal Medicine

Background:

• Human pregnancies with placental dysfunction can exhibit an elevated hyperoxic Blood oxygen level-dependent (BOLD) MRI response.
• The underlying pathophysiology of this phenomenon requires further investigation.
• This study explores the association between altered placental baseline conditions and the BOLD MRI response.

Purpose of the Study:

• To evaluate if a high hyperoxic BOLD MRI response in pregnancies with placental dysfunction is linked to altered placental baseline conditions.
• To assess placental oxygenation and tissue morphology using transverse relaxation time (T2*).

Main Methods:

• Utilized dynamic and multi-echo gradient-recalled echo (GRE) MRI sequences during maternal oxygen inhalation.
• Measured relative ΔBOLD response and absolute ΔT2* in 49 normal pregnancies and 13 pregnancies with placental dysfunction.
• Placental dysfunction was defined by low birth weight (<10th percentile) and pathological signs of vascular malperfusion.

Main Results:

• The relative ΔBOLD response was significantly higher in pregnancies with placental dysfunction compared to controls.
• No significant difference was found in the absolute ΔT2* (placental oxygenation increase) between groups.
• A lower baseline T2* was observed in cases, indicating altered placental baseline conditions, and a strong negative correlation was found between Log10 ΔBOLD response and baseline T2*.

Conclusions:

• The exaggerated hyperoxic ΔBOLD MRI response in placental dysfunction may be attributed to altered placental baseline conditions.
• The absolute increase in placental oxygenation (ΔT2*) does not differ between normal and dysfunctional placentas.
• Baseline placental T2* is a potential indicator of altered placental morphology and oxygenation in dysfunction.