The test is generally done at one and five minutes after birth, and may be repeated later if the score is and remains low. Scores 3 and below are generally regarded as critically low, 4 to 6 fairly low, and 7 to 10 generally normal.
A low score on the one-minute test may show that the neonate requires medical attention[3] but is not necessarily an indication that there will be long-term problems, particularly if there is an improvement by the stage of the five-minute test. If the Apgar score remains below 3 at later times such as 10, 15, or 30 minutes, there is a risk that the child will suffer longer-term neurological damage. There is also a small but significant increase of the risk of cerebral palsy. However, the purpose of the Apgar test is to determine quickly whether a newborn needs immediate medical care; it was not designed to make long-term predictions on a child's health.[1]
A score of 10 is uncommon due to the prevalence of transient cyanosis, and is not substantially different from a score of 9. Transient cyanosis is common, particularly in babies born at high altitude. A study comparing babies born in Peru near sea level with babies born at very high altitude (4340 m) found a significant difference in the first but not the second Apgar score. Oxygen saturation (see Pulse oximetry) also was lower at high altitude.[4]
Just why they are done, I had a table but it wont work here