Outline of a typical IVF cycle
IVF involves four basic steps; ovarian stimulation, egg collection, insemination and finally embryo transfer.
During a natural unstimulated cycle, a single follicle containing a single egg develops to maturity. It is possible to perform IVF using a single egg from a natural cycle, but the success rates with this are low. Hence, most IVF cycles involve stimulation of the ovaries with medicines known as gonadotrophins to produce multiple eggs. About thirty six hours before the egg collection is due, an injection of human chorionic gonadotrophin (hCG) is given to initiate the final process of egg maturation.
This is done under sedation or general anaesthetic using a vaginal ultrasound probe. A needle is guided through the top of the vagina into the ovary. The fluid is drawn out of each follicle through the needle using a suction device.
The male partner is asked to produce a semen sample, this is prepared in the laboratory, with the healthiest sperm being used for IVF.
The sperm and eggs are placed together, it takes about eighteen hours for fertilisation to be completed and about twelve hours later the embryo will start to divide.
In two to three days after egg collection, embryos have usually divided into four to eight cells. They can continue to be grown in the laboratory beyond this, up to six days after egg collection. At this stage, the embryo should form a blastocyst.
The healthiest embryos are chosen for transfer, the transfer is an important step and is often performed under ultrasound guidance. The procedure is virtually painless.
Any spare good quality embryos can then be frozen for use in the future. A frozen embryo can be thawed and transferred into the uterus either as part of the natural cycle (unstimulated cycle) or as part of a cycle controlled by hormone treatment (stimulated cycle).
If an embryo successfully attaches itself to the inside of the uterus and continues to grow, the result is a pregnancy.
Completing all these steps, including any subsequent frozen embryo transfers is one full cycle of IVF treatment, as defined by the National Institute for Health & Care Excellence
A cancelled IVF cycle is defined by NICE as ‘one where an egg collection procedure is not undertaken’. If a cycle is cancelled in this way then it will not count as a cycle and would not be included when considering the number of eligible cycles offered. However, if the cycle is cancelled due to low ovarian reserve NICE says that cancelled cycles ‘should be taken into account when considering suitability for further IVF treatment.’
An abandoned cycle is not defined by NICE, but in terms of NHS treatment if egg collection is undertaken then this is would normally be considered a ‘full cycle’, and would be included when considering the number of eligible cycles offered.
Funding for NHS fertility treatment varies across the country, with access entirely dependent on your postcode. Although there is national guidance set by NICE (2013) local priorities within the NHS can decide the level of funding, and will determine the number of cycles and frozen embryo transfers funded and what additional criteria a patient has to meet in order to qualify for treatment.
For more information on funding please visit the NHS Funding section.