(CNN)In the 1930s and 1940s, Dr. Virginia Apgar noticed something odd. Despite the US infant mortality rate decreasing overall, a high number of infants were still dying within 24 hours of birth.
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Part of the problem was that there was no standard of comparison for newborns; babies often went home with undiagnosed problems.
Apgar challenged this practice and set the foundations of neonatology when she created the Apgar score in 1952, according to the US National Library of Medicine. The scoring system, which has since saved countless babies, evaluates newborns' health on five factors: heart rate, respiration, skin color, muscle tone, and reflexes.
The test is conducted in the first five minutes after birth, allowing doctors to determine which babies need immediate care.
Apgar even linked the scores to infant mortality; the lowest-scoring babies had a mortality rate of 14%, compared to 0.13% for the highest-scoring babies.
The Apgar score was quickly adopted by hospitals across the US, and is credited for lowering the national infant mortality rate. It later spread worldwide.