First off, countries define child mortality differently.
This does not mean it was 10 times worse in the US.
In the US we would count a baby that died in the womb as a dead baby in these stats, some countries don’t count them unless a few days has passed since birth.
Apples and oranges.
1935 55.7 per 1000
2000 6.9 per 1000
This is a comparison within the United States and has nothing to do with Ireland except to show the decline, thankfuly steep, in infant mortality.
The terms neonatal, post-natal, and newborn all refer to living infants. Children are much older and a different subject altogether. However I have seen statistics lumping everyone up to the age of five together.
How Ireland defines infant mortality was of no concern and I should not have considered because my main point was the decline in infant mortality in the U.S.since 1935. The U.S. stats do show, which as you point out, includes such causes as intrauterine hypoxia and birth asphyxia.