Not 50 but I delivered a baby at 48 (via DE) as a single mother. I had an easy pregnancy, C-section (only because baby was too big), and easy recovery. I don't feel too old myself and I have enough energy even as a single parent with no household help (and I don't need lots of sleep). My kid is VERY active too and a night owl

!
Motherhood is a beautiful, fulfilling experience for me and I am so happy that I did it, despite the all the negative press, nay-sayers, etc. Sure I do worry about getting sick and dying young but so do my younger friends. I just try to stay fit and I am on top of health check-ups, more so than before.
I have to admit, despite my joy I do worry about being alive "long enough" to raise my son through his 20s and hopefully beyond but I did create a LIFE... a beautiful happy child that otherwise would have never been born!
A bit of advice -- don't advertise your age to anyone, especially your young new mom friends... nobody's business, just go with the flow. and do what you can to look younger (dress, skin...) because it will make you feel better about your age if you start to feel old.
good luck!
(Yes, I meet plenty of first time dads in their 50s but no one gives a crap... double standard. Same for older celebrity moms like Sandra.)