In the context of IVF, HCG is used to trigger ovulation in women undergoing assisted reproductive technology. This is because HCG mimics the actions of LH (luteinizing hormone), which is normally responsible for triggering ovulation in a natural menstrual cycle.
After a woman has been given follicle-stimulating hormones (FSH) to stimulate the growth of multiple follicles in her ovaries, HCG is given as a final injection to trigger the final maturation of the eggs within the follicles. This timing is important because the eggs need to be at the right stage of maturation for retrieval during an IVF procedure.
HCG is usually given when a woman has two or more mature follicles on an ultrasound scan. It is usually given around 36 hours before egg retrieval, which allows the eggs to reach the appropriate stage of maturity. The injection is typically given in the evening and egg retrieval is scheduled for 36 hours later.
After the HCG injection, the eggs are collected from the ovaries through a transvaginal ultrasound-guided aspiration. The eggs are then fertilized in the laboratory with sperm from the male partner or a donor, and the resulting embryos are transferred to the woman's uterus.
In summary, HCG is an important hormone used in IVF to trigger ovulation and ensure that the eggs are at the appropriate stage of maturity for retrieval. It is typically given as a final injection before egg retrieval and helps to increase the chances of a successful IVF procedure.