I just rolled out of bed and haven't had coffee yet, but isn't your source saying that the illegitimacy rate was 2 to 4% in England in the late 1700s and that 37% of first pregnancies were 'conceived' before marriage? *"" For example, while only two to four percent of births in England in the late 1700s were illegitimate, thirty-seven percent of first births to a couple followed pre-marital conception.""*
Besides that isn't about the female marriage rate anyway.
Here is another link to Google books.
And I guess you are right, it isn’t just about the female marriage rate. My point was that there were times with high rates of illegitimate children in Western countries before now.