If you haven't gone through menopause, you could still get pregnant at that age. I don't know how healthy it would be for a mother or the child... And socially it would be very awkward to have a 53 year old mother taking you to school. Then at graduation the mother would be 66. Paying for college and trying to retire would be incredibly difficult - not to mention all the energy it takes raising a kid.
It is possible and women are having babies in their 50s but personally I don't think it is fair to the child. At 48 you may still feel young but think about the child who will possibly lose their parent at such a young age when they need them the most: graduating from high school, going to college, getting married and everything else that comes with life. There is also a big possibility of having a child with downs syndrome at 48.
I see lots of grandparents (age 55 and over) doing the school run now and childminding because the parents who are in their twenties or thirties are too busy with their careers to care for their own kids and so dump them on grandparents. Older mothers (and I am one) have more money, have done the career thing and want to spend quality time with their much wanted kids. Young parents can die too. If you want and can have a child in your forties you are probably very healthy in the first place and taking care of yourself.