All IVF treatments begin with a course of hormone therapy to stimulate the development of several follicles in the ovary. These are collected as eggs, which are then fertilised to create several embryos. After between two and five days in an incubator, one or two of these embryos are transferred through the vagina to the uterus, where implantation occurs and pregnancy begins. However, in IVF as in natural conception, not every embryo implants to become a pregnancy, which is why surplus embryos are frozen - so that a subsequent transfer might be tried if the first one fails. Freezing is now an essential part of every clinic's IVF programme.
Because the transfer of two or more embryos is associated with multiple pregnancy, there has been a determined effort in recent years to cut this multiple rate by transferring just one embryo and freezing the remainder. At the LWC we encourage single embryo transfer in patients with a good chance of success.
The most widely reported 'side effect' associated with IVF is a multiple pregnancy. There is also a very small risk that some women (1-2%) will over-react to the hormone drugs used to stimulate the ovaries (OHSS), but ultrasound and hormone monitoring during this drug treatment phase usually ensures that any over-reaction is foreseen and any risk avoided. Egg collection can be uncomfortable, and is often performed with a local anaesthetic.
As with any type of fertility treatment, success rates in IVF will vary according to patient age and other circumstances. The LWC’s pregnancy and live birth rates from IVF are recorded by the HFEA and can be found here.