Which interspace is safest for lumbar puncture in extremely preterm infants to avoid cord penetration?

• A. L2-L3 interspace
• B. L3-L4 interspace
• C. L4-L5 interspace
• D. L5-S1 interspace

Answer: (C)

In extremely preterm infants the spinal cord ends higher in the canal than in older children or adults, so choosing a level below where the cord terminates reduces the risk of penetrating neural tissue during a lumbar puncture. The conus medullaris in these babies typically ends around L2–L3, making the L4–L5 interspace the safest target to access the subarachnoid space without hitting the cord. Higher levels like L2–L3 or L3–L4 carry a real risk of cord penetration, while L5–S1 is lower but not the standard preferred site for reliable CSF access in this population. Hence, L4–L5 is the best choice.