Normal Developmental Globe Morphology on Fetal MR Imaging

Area of Science:

• Fetal imaging and developmental biology.
• Ophthalmology and radiology.
• Human embryology and anatomy.

Background:

• Fetal globe morphology undergoes age-dependent structural changes during gestation.
• Early gestation features conical globes with bulging posterolateral margins.
• Later gestation shows a transition to ellipsoid globe shapes.

Purpose of the Study:

• To establish normal developmental fetal globe morphology.
• To define age-specific criteria for fetal globe shape.
• To differentiate normal fetal eye development from potential abnormalities.

Main Methods:

• Retrospective analysis of fetal MRI scans from an academic children's hospital.
• Inclusion criteria: 17-39 weeks gestation, exclusion of malformations and artifacts.
• Evaluation of globe shape (elliptic/nonelliptic) and hyaloid visibility by two neuroradiologists.

Main Results:

• Age strongly predicts globe shape (AUC=0.99) and hyaloid visibility (AUC=0.94).
• Non-elliptic globes are typical up to 22 weeks; elliptic shapes dominate after 29 weeks.
• Hyaloid vasculature is visible up to 19 weeks, gradually disappearing by 25 weeks.

Conclusions:

• Nonspheric fetal globe shapes are physiologically normal until 29 weeks gestation.
• Elliptic globe shapes are characteristic of fetuses at 29 weeks and older.
• These developmental changes correlate with the resolution of the primary vitreous.