In vitro fertilization, IVF. Form of insemination, extracorporal fertilization of a human egg cell in a nutrient solution. To perform an IVF, mature egg cells are extracted out of the (hormonally stimulated) ovary by a puncture or a laparoscopic procedure, then the sperm is added. Ca. 48 - 72 hours after fertilization, 3 -4 embryos (4 to 8 cell stage) are inserted into the uterus, their nidation being supported by giving hormones. The IVF is a method for women whose natural pathway between uterus and ovaries is impaired or even non-existent.