My mother-in-law was 47 when my husband was born, and they had a wonderful relationship. He has older siblings as well. But my oldest son's best friend (they are both six) is an only child. Her mother was 42 when she gave birth, 41 when she got pregnant for the first and only time. And they did not use any fertility treatments. I was 24, and though I think I had more energy (and still do, on baby number four) this little girl and her parents have a fabulous relationship, and they are very glad they waited until they did to have her. At the preschool where I teach 2-year-olds, we have three moms out of the 12 who are over forty, and only one under thirty. I think mid-to-late 30's is getting to be the average these days. Good luck! It's wonderful!