In vitro fertilisation (IVF): technician placing a petri dish containg fertilised ova into an incubator. 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 in a petri dish, 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.