IVF treatment can be broken down into three separate phases:
– The stimulation of the development of several eggs
– The collection of the eggs and their fertilisation in the laboratory by your partner’s sperm
– The transfer of the resulting embryos into your uterus
Step 1: The stimulation of the development of several eggs
Normally the human ovary is designed to produce one egg a month. However, if you are undergoing in vitro fertilisation treatment and only one egg is available, the chances of pregnancy are fairly slim. It is therefore important to cause several eggs to develop simultaneously within the ovary.
This is achieved by giving you daily injections of a hormone (FSH) which is the same hormone your brain naturally produces to stimulate your ovaries. Because you are receiving higher doses of this hormone than your brain would normally produce, more than one egg develops.
The number and maturity of eggs that you are producing is assessed by ultrasound examination of the ovaries. The ultrasound does not show the eggs themselves but the fluid filled structures (follicles), which contain the eggs. This is performed at intervals during the treatment.
Typically, you would have approximately four ultrasound scans over the course of your treatment cycle. When the scan shows that the follicles, and therefore the eggs, are properly mature you will be scheduled to have a late evening, a trigger injection is given to cause the final ripening of the eggs. The eggs will be collected thirty-seven hours later
Step 2: The collection of the eggs and their fertilisation in the laboratory by your partner’s sperm
Egg collection is performed thirty-seven hours after the trigger injection.
The eggs are recovered using ultrasound through the vagina. A fine needle is passed through the ultrasound probe directly into the ovarian follicles and the eggs are gently sucked out.
This procedure is performed under sedation administered by an anaesthetist. You will not be aware of the procedure taking place although the sedation is not as strong as a general anaesthetic. Typically, the egg collection lasts fifteen to twenty minutes. It is usually possible to collect eggs from between 80-100% of the larger follicles. The eggs are inspected in the laboratory for a preliminary idea of their maturity. Quality, rather than quantity, is important at this stage.
Your partner will accompany you to the clinic and his sperm must be produced on the morning of egg collection.
The eggs and his prepared sperm will be mixed together in the laboratory in carefully controlled conditions. If the sperm quality is low and ICSI is necessary, the sperm will be microinjected into each mature egg at this time
It takes twenty-four hours to find out if the eggs have been fertilised. If so, they are allowed to develop for a further one or two days to become embryos. It is only at this stage that they can be transferred into the uterus.
Step 3: The transfer of the resulting embryos into your uterus
Embryos are transferred back into the uterus three – five days after the day of egg collection.
This is a very important stage of the treatment and the skill with which the embryo transfer is performed is critical in determining the success of treatment. The embryo transfer is usually a completely painless procedure similar to having a cervical smear test.
The embryos are placed in the middle of the cavity of the uterus and the procedure takes just a few minutes. The embryos do not implant (embed) in the uterus straight away. This only occurs three or four days later but there is no danger of them dropping out of the uterus when you stand up!
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