How is it that John Denver had Jesse Belle when he proclaimed to be sterile during his first marriage?

Reportedly, his sterility was the result of a low sperm count. Few medical options for treating low sperm count infertility were available during the years he was married to Annie. By the time he married Cassandra, there were new medical possibilities like in vitro fertilization (IVF). I vaguely recall hearing of a procedure to "strain" and concentrate sperm to help couples conceive. Lots of incredible work was being done to achieve biological children for previously infertile couples. What difference does it make to anyone now which of the procedures worked for them? It is just such a wonderful thing that options opened up to couples. It is also a miracle that the lack of fertility contributed to the blessing that he and Annie experienced in adopting their beloved children. Many of us believe that things happen for a reason, and in the time they are meant to happen.