The chance of a positive pregnancy test after a fresh cycle of IVF varies but is approximately 20 to 30 per cent. In order to maximize the chances of a pregnancy, two embryos are usually returned at the same time which is why there is an increased chance of twin pregnancies. If sufficient embryos of good quality develop there may be an option to freeze them and replace them, after thawing, in a subsequent cycle. The success of such a frozen embryo transfer is slightly less than that of a fresh cycle. The availability of IVF on the National Health Service varies considerably from one part of the country to the other.
Couples often have to be prepared to pay to have their treatment at a private hospital.
However, with ICSI a single sperm is injected into a single egg in the laboratory. Normally sperm is obtained by masturbation. Under certain circumstances sperm may be obtained directly from the testis by a minor operation. Sperm is inseminated into the womb after ovulation has been precisely timed. The donor must be prepared to undergo stimulation of the ovaries with drugs and egg collection as if she were undergoing IVF herself.