I know 39 is the new 25, but she was a bit old to be getting preggers.
Always good to hear from the informed. 4th child at 40 not at all unusual.
My mother was 37 when I was born and 39 when my very intelligent brother was born ...
35+ y/o is considered a “geriatric pregnancy”.
https://my.clevelandclinic.org/health/diseases/22438-advanced-maternal-age