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Updated: May 16, 2026
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Human Fetal Blood Flow Quantification with Magnetic Resonance Imaging and Motion Compensation
Published on: January 7, 2021
Normal ascent of the conus medullaris: a post-mortem foetal MRI study
O J Arthurs1, S Thayyil, A Wade
1Great Ormond Street Hospital for Children, London, WC1N 3JH, UK. owen.arthurs@gosh.nhs.uk
Summary
The conus medullaris normally ascends throughout fetal development. Most fetuses reach the adult conus position by 33 weeks gestation, with significant ascent observed with increasing gestational age.
Area of Science:
- Developmental anatomy
- Fetal imaging
- Neurology
Background:
- The conus medullaris's position is critical for spinal cord health.
- An abnormal conus position below lumbar vertebrae three (L3) at birth is a diagnostic concern.
Purpose of the Study:
- To investigate the timing of normal conus medullaris ascent during fetal development.
- To establish normative data for conus medullaris position using fetal MRI.
Main Methods:
- Utilized 3D magnetic resonance imaging (MRI) on 84 post-mortem fetuses (14-41 weeks gestation).
- Assessed conus medullaris position using a numerical scale for vertebral levels (S2 to T12).
Main Results:
- Conus medullaris ascent significantly correlated with increased gestational age.
- By 20 weeks, 84.2% of fetuses had a conus at L4/5 or higher; only 22.8% were at L3 or higher.
- By 40 weeks, 94.8% of fetuses reached the L3 level, with 50.7% reaching L3 by 26 weeks.
Conclusions:
- Regular ascent of the conus medullaris occurs throughout fetal life.
- While individual fetal growth may be non-linear, the majority achieve a normal adult conus level by 33 weeks gestation.
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