I think 19 is probably a little above average. But I’m thinking that all my forebears of the late 19th century were in families that had 10-12 children and, in the case of both my grandparents, 12 children. Now of all these great-aunts and -uncles, most of them did not have nearly as many children (although my grandmother* had 10) and some of them never married or never had any. So the average was much less.
I find the idea quite exhausting, myself. But I think most healthy women could probably do it if they wanted to.
*Who got married in 1904, when she was 16, and had her first baby in 1906 and her last one in 1929. One of my aunts and one of my uncles were less than a year apart in age, and always in the same grade.