Fertility treatment steps
Indications for its use include:
However, depending on the exact protocol being used, not all the stages are used:
This is believed to have three potential functions:
This temporarily stops the pituitary gland from functioning which reduces the risk of a cycle being cancelled from early exposure to luteinising hormone (LH) which could disrupt normal follicle and oocyte development or stimulate premature release of the eggs before they can be retrieved surgically (‘harvested’) prior to insemination in the laboratory.
The aim of this stage is to produce a number of mature eggs which can be retrieved surgically prior to fertilization in the laboratory.
At the end of the stimulation phase of an IVF cycle, a drug (‘ovulation trigger’) is used to mimic the natural endogenous LH surge which initiates the process of ovulation. The mature eggs are collected from the woman (‘harvested’) and fertilised with sperm in a laboratory.
After triggering, mature oocytes are aspirated from the woman’s ovaries for fertilisation in the laboratory. In addition, in some cases of male factor infertility the sperm has to be obtained directly from the testes.
Once the eggs have been fertilized, one or two of the resultant embryos are then placed back into the woman’s uterus 2–3 days later, at the cleavage phase of embryo development. Longer laboratory culture times can be used with good quality eggs with intra-uterine replacement occurring after 5–6 days, at the blastocyst phase of development.
After embryo replacement, drugs may be given to help support the early phase of pregnancy development. This is intended to mimic what happens in natural conception, where, once ovulation has occurred, the endometrium prepares to receive a fertilised embryo. This consists of a series of changes within it which are driven by progesterone produced by the corpus luteum in the ovary. An IVF cycle may be stopped (‘cancelled’) at various points within the treatment process. A cycle will most often be cancelled either because the treatment presents a risk to the women (for example ovarian hyperstimulation syndrome [OHSS]) or because the woman has not responded to part of the treatment (for example ovarian stimulation), and this most frequently occurs during ovarian stimulation; that is, before oocyte retrieval. However, in some circumstance oocytes may be collected and frozen for later transfer. This may be construed as interruption of the fresh IVF cycle rather than cancellation as the intention is to transfer embryos at a later date.