In someways you're probably not totally safe until mid-50's. I hadn't had a period for years due to mini pill, came off that and on to HRT as blood test showed I was an earlyish meno, then low and behold 18 months later had sore boobs, cramps and a period arrived! Of course the medics went into mass panic but that's all it was. Probably the hrt just gave me enough hormones to crank up the system again!
Both my great grans had kids in their late 40's which I bet was fairly common without contraception back then. I know someone who was told it was meno, was 4 months gone, nature's last hurrah!