How big can the follicle be for IVF?

With the development of medicine, some women who cannot ovulate normally can still have their own children through in vitro fertilization, and the success rate of in vitro fertilization is getting higher and higher. To have an IVF procedure, women must have high-quality eggs, but how big of a follicle can be retrieved? The follicles must be mature before they can be retrieved, and follicles larger than 10mm in diameter can be retrieved.

The follicle is the basic unit that maintains female physiological functions. The follicles secrete sex hormones to maintain female body shape, sexual function, and the health of the cardiovascular and skeletal systems. The normal growth of follicles is complexly affected by the ovarian function itself, the hypothalamus-pituitary-ovarian axis, the central nervous system, and the endocrine system.

In medicine, when the diameter of a follicle is >10mm, it is called a dominant follicle; when the diameter of a follicle is >18mm, it is called a mature follicle. The diameter of a mature follicle is generally between 18 and 20mm.

Natural ovulation process

Natural ovulation is a process in which the mature follicle develops to a certain stage and clearly protrudes from the surface of the ovary. As the follicular fluid surges and the internal pressure rises, the protruding ovarian tissue becomes thinner and thinner, and finally ruptures. The secondary oocyte and its surrounding zona pellucida and corona radiata are discharged from the ovary along with the follicular fluid.

IVF ovulation process

During the ovulation induction stage of in vitro fertilization, patients need to take medication to promote the growth of follicles. When the follicles grow to a certain stage, they need to take night injections (usually human chorionic gonadotropin (HCG) or short-acting gonadotropin-releasing hormone agonist (GnRH-a)) to promote the final maturation of the oocyte, allowing the mature follicle to eventually rupture and discharge the mature egg.

Although there are some differences between natural ovulation and IVF ovulation, the eggs must be mature follicles when ovulating or retrieving eggs. Therefore, when retrieving eggs for in vitro fertilization, the size of the follicles should be approximately between 18 and 28 mm.

Test tube instructions

However, during the IVF treatment, we also need to refer to the time of the night injection when retrieving eggs. Generally, we retrieve eggs about 36 hours after the night injection. Assuming that you receive the night injection at 9:00 p.m. on the 10th, after 36 hours, the best time to retrieve the eggs will be around 9:00 a.m. on the 12th, no more than an hour before or after.

Here, we recommend that patients relax, which will also help improve endocrine status and promote the development of follicles. During the ovulation induction phase, try to cooperate with the doctor's treatment, monitor the follicles on time, follow the doctor's advice, and wait for the right time to get the night injection and wait for egg retrieval.