In vitro fertilisation (IVF) is a process by which egg cells are fertilised by sperm outside the womb, in vitro. IVF is a major treatment for infertility when other methods of assisted reproductive technology have failed. The process involves hormonally encouraging ovulation, harvesting ova (eggs) from the ovaries followed by fertilisation in a fluid medium. The fertilised egg (zygote) is then transferred to the patient's womb with the intent to establish a successful pregnancy.

Process

Ovarian stimulation
Treatment cycles are typically started on the third day of menstruation and consist of a
regime of fertility medications to stimulate the development of multiple follicles in the
ovaries. In most patients injectable gonadotropins (usually FSH analogues) are used under close monitoring. The estradiol level is monitored and follicular growth is assessed by gynaecologic ultrasonography,. Typically approximately 10 days of injections
are needed. Spontaneous ovulation during the cycle is typically prevented by the use
of GnRH antagonists, which block the natural surge of luteinising hormone (LH).

Egg retrieval

Once adequate follicular maturation is achieved, human chorionic gonadotropin (hCG) is
given. This agent, which acts as an analogue of luteinising hormone, in initiates ovulation about 42 hours after injection, the eggs are retrieved from the ovary. The eggs are retrieved from the patient by a transvaginal technique involving an ultrasound-guided needle piercing the vaginal wall to reach the ovaries. Follicles are aspirated through the needle, and the follicular fluid is handed to the IVF laboratory to identify ova. It is common to remove between ten and thirty eggs. The retrieval procedure takes about 20 minutes and is usually done under conscious sedation or general anaesthesia.

Fertilisation

In the laboratory, the identified eggs are stripped of surrounding cells and prepared for
fertilisation. In the meantime, semen is prepared for fertilisation by removing inactive cells and seminal fluid. If semen is provided by a sperm donor, it would have been prepared for treatment before being frozen and quarantined, and it will be thawed ready for use. The sperm and the egg are incubated together at a ratio of about 75,000:1 in the culture media for about 18 hours. In most cases, the egg would be fertilised by that time and the fertilised egg would show two pronuclei. In certain situations, such as low sperm count or motility, a single sperm may be injected directly into the egg using intracytoplasmic sperm injection (ICSI). The fertilised egg is passed to a special growth medium and left for about 48 hours until the egg consists of six to eight cells.
In gamete intrafallopian transfer, eggs are removed from the woman and placed in one of the fallopian tubes, along with the sperm. This allows fertilisation to take place inside the woman's body.

Risk

The major complication of IVF is the risk of multiple births. This is directly related to the
practice of transferring multiple embryos at embryo transfer. Multiple births are related to increased risk of pregnancy loss, obstetrical complications, prematurity, and neonatal
morbidity with the potential for long term damage.
Ovarian stimulation is associated with the risk of ovarian hyperstimulation syndrome.
If the underlying infertility is related to abnormalities in spermatogenesis, it is plausible, but too early to examine that male offspring is at higher risk for sperm abnormalities.