Why do we need so many sperm?

Happy 2019!  Looking back at my blogs, it seems the most popular ones are the simplest.  The ones where I attempt to explain the every day questions of infertility.  Sure, chatting about fancy lab treatments like PGT-A is exciting, but most people are hoping they will never need a "fancy lab treatment" to get pregnant.  They have good questions about the basics of getting pregnant, or not.

Frozen Versus Fresh

During IVF treatment, we fertilize eggs with sperm to make embryos. Traditionally, we would transfer embryos into a woman's uterus a few days after fertilization, while they are "fresh," not frozen. If there are more embryos than those being transferred, i.e. surplus embryos, we freeze them. When I started my practice, we were slow-freezing those surplus embryos and their pregnancy rates were about 60% of the rates of the fresh embryo pregnancies.