Symptoms of HIE typically evolve over approximately how many hours after birth?

• A. 12 hours
• B. 24 hours
• C. 48 hours
• D. 72 hours

Answer: (D)

Hypoxic-ischemic injury to the newborn brain doesn’t peak all at once. After the initial insult, there is a latent period followed by secondary energy failure that brings progressively worsening neurologic signs over the next day or two, often peaking around 72 hours after birth. That extended progression over about three days is why 72 hours is the best fit. Early signs may appear within the first day, but the characteristic evolution continues to develop through the first 2–3 days, highlighting the importance of ongoing monitoring and neuroprotective care during that period.