Embryo freezing: Embryo freezing is the best-studied and most widely used form of fertility preservation. Embryos are obtained through an advanced fertility treatment called in vitro fertilization (IVF). IVF has resulted in millions of live births in women and men with infertility. The ovaries are stimulated with injections of hormones that stimulate follicles on the ovaries to produce mature eggs. The process is closely monitored during 1-2 weeks of ultrasounds and blood draws.