In vitro fertilisation (IVF). Light microscope image of a tiny human ovum being sucked into a pipette for transfer to a petri dish for fertilis- ation. In IVF, fertility drugs are given to potential mothers to stimulate the production of several ova, rather than the usual one. These are then harvested, usually by laparoscopy, and are fertilised using a fresh or frozen sample of the husband's sperm. If fertilisation is successful, the embryos are incubated for up to 42 hours and then transferred back into the woman's uterus via a catheter inserted through the cervix. 3-4 embryos are often introduced to increase the probability that one will implant.