Being a mother at the age 50 is not the problem here. (Of course it has been much rarer, as a genealogist, over the 30 years I have stumbled upon several mothers over 50yrs)
Finland's oldest mother was 58 years old, and she had a baby before fertility treatments were invented. https://www.hs.fi/kuukausiliite/art-2000005473243.html
Although in Europe the spike in childbearing was often 15-20 years old and the 16th century was a dangerous time for a woman’s health, older mothers have always existed. At 1920s, about 1,000 mothers became mothers each year, the number of births over the age of 50 did not decline until the 1960s. At present, it is historically unique that one third of Finns over the age of 50-mothers, are first-time mothers, as they have previously been mothers of a large family.
The only problem here is the missing source.