I don't suppose you might have a link to a study to support this statement? The way variations of this comment always appear without any sort of evidence or substantiation has made me think that it might me a popular misconception...
Here's the first one I found by searching for 'life expectancy by age'. You can see that child mortality was indeed very large, but adult mortality has also declined sharply e.g. a 20-year-old white male today can expect to live 15 years longer than his counterpart in 1900:
