Evaluating fetal head dimension changes during labor using open magnetic resonance imaging

Area of Science:

• Obstetrics and Gynecology
• Medical Imaging
• Fetal Biomechanics

Background:

• Fetal skull molding is crucial for vaginal delivery, enabling the head to adapt to the maternal pelvis.
• The biomechanics of fetal head adaptation during labor are not fully understood.
• Real-time visualization of this process can provide novel insights.

Observation:

• Open magnetic resonance imaging (MRI) was used to observe a human birth in real-time.
• Cinematic MRI series captured the fetal head's configuration during the second stage of labor.
• Measurements of the frontooccipital diameter (FOD) and vertex-to-base distance were analyzed frame-by-frame.

Findings:

• In an occiput anterior position, the fetal frontooccipital diameter (FOD) increased from 10.3 cm to 11.2 cm during expulsion.
• The distance from the fetal vertex to the skull base decreased from 6.4 cm to 5.6 cm.
• These changes indicate significant deformation and elongation of the fetal skull during vaginal delivery.

Implications:

• This study demonstrates the utility of real-time MRI in visualizing the biomechanics of fetal head molding.
• The findings provide a clearer understanding of fetal head changes during the late second stage of labor.
• Advanced imaging can help define the dynamic alterations in fetal head dimensions during the birthing process.