How to give the night injection for IVF

In fact, although many people often hear about people getting pregnant through in vitro fertilization, most people don’t know the specific operation process of in vitro fertilization or its principles. In fact, IVF surgery is a very complicated and long process, so before doing it, you must think carefully and understand some basic situations. So how should the night injection be given when doing in vitro fertilization?

What is downregulation in IVF?

Many women who are preparing to have a test-tube baby have heard of the term "night injection". Before egg retrieval, the doctor will use ovulation-stimulating drugs to help the female ovaries super-ovulate, so that multiple eggs can develop and mature in order to form multiple embryos. When the follicles are close to maturity, special drugs are needed to help the follicles finally mature. This process is called "night injection".

Generally speaking, in the final stage of ovulation induction, women need to inject human chorionic gonadotropin (HCG), and some people also inject short-acting gonadotropin-releasing hormone agonist (GnRH-a). Since the injection time is usually scheduled at night, we generally call the down-regulation step "night injection."

So, why is the night shot done by injecting HCG?

Ovulation is the process by which the follicle cells and the surrounding cumulus granulosa cells are discharged together. Before ovulation, the mature follicles secrete estradiol, which causes a large amount of GnRH to be released from the hypothalamus, which in turn causes the pituitary gland to release gonadotropin, resulting in an LH peak. The LH peak generally occurs 36 hours before the follicle ruptures. After that, the LH peak works together with progesterone to activate the activity of endogenous proteases, forming an ovulation hole and inducing ovulation. The chemical structure of HCG is similar to that of LH, and it can simulate the LH peak before ovulation, stimulating follicle maturation and ovulation.

The timing of the night injection is very important. If the HCG injection is too early, the morphology and function of the follicles will not be fully mature, their developmental potential will be affected, and there will not be enough LH receptors on the granulosa cells of the follicles, and they will not be able to respond appropriately to HCG. If the HCG injection is too late, the egg cells may have matured, their quality may have decreased, or they may have been expelled. At this time, the night injection may lead to increased progesterone and the risk of ovarian hyperstimulation syndrome. Therefore, the time for night injection is different for each person. The doctor will determine the specific time for night injection based on the number, size and hormone levels of the patient's follicles. Since the egg will mature and be released about 36 hours after the LH peak, in order to be able to retrieve the egg in the morning when the physical condition is better, the night injection is usually scheduled in the evening.