Assisted conception. II—In vitro fertilisation and intracytoplasmic sperm injection
BMJ 2003; 327 doi: https://doi.org/10.1136/bmj.327.7419.852 (Published 09 October 2003) Cite this as: BMJ 2003;327:852
- Peter Braude,
- Paula Rowell, senior embryologist
- Guy's and St Thomas's assisted conception unit, London
Introduction
In vitro fertilisation (IVF) and intracytoplasmic sperm injection (ICSI) are two of the main types of assisted conception that take place in the laboratory. This article covers these two techniques in detail and looks at their safety and success.
Fertilisation: (left) each egg is surrounded by a complex of cumulus cells (purple) that the sperm need to disperse to reach the zona pellucida, the protective outer coating of the egg; (middle) capacitated sperm first bind to the zona pellucida (1) and release enzymes from the acrosome (2), which digest a pathway through the zona pellucida (3); (right) the sperm is able to fuse with the plasma membrane of the egg and becomes incorporated within the egg
In vitro fertilisation
In IVF, oocytes (obtained surgically from ovarian follicles in superovulated cycles) and prepared sperm are brought together in a dish in the laboratory. Fertilisation takes place outside the body (in vitro = in glass). Cleavage stage embryos derived from these fertilised oocytes are placed in the uterus (embryo transfer) for pregnancy to occur.
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Indications for IVF
The process
Superovulation
Patients receive superovulation treatment with gonadotrophins, usually preceded by pituitary suppression with gonadotrophin releasing hormone analogues (see last week's article). A careful balance is needed to maximise safely the number of oocytes retrieved. Ideally, there should be a choice of embryos for transfer, and some embryos should be available for cryopreservation. However, the risk of ovarian hyperstimulation syndrome also needs to be minimised. Ultrasonography of the ovaries and in some cases monitoring the rise in plasma estradiol concentration are used to check the effect of superovulation. Administration of human chorionic gonadotrophin is scheduled when the leading follicles are≥18 mm in diameter, and given 34-38 hours before planned egg retrieval. About 10% of cycles are cancelled before the planned egg collection because the response to superovulation is excessive and …
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