Oocyte cryopreservation, commonly known as egg freezing, is a medical procedure used to preserve a person’s fertility for future use. The process involves stimulating the ovaries to produce multiple eggs, which are then retrieved and stored. While the act of freezing the eggs themselves has no effect on the body’s long-term function, the necessary medical preparation temporarily interrupts and manipulates the natural menstrual cycle. The temporary absence of a typical period is a direct result of the high-dose hormonal medications used during the two-week treatment phase.
Hormone Treatment and Cycle Suppression
The temporary suppression of the natural cycle occurs during the ovarian stimulation phase, which typically lasts between 10 and 14 days. This phase begins with the administration of injectable hormones designed to override the body’s inherent reproductive rhythm. Patients receive high doses of gonadotropins, which are analogs of follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
These exogenous hormones force the ovaries to mature multiple egg follicles simultaneously, instead of the single dominant follicle that develops naturally. To prevent premature release, a second type of medication is introduced, often a Gonadotropin-Releasing Hormone (GnRH) agonist or antagonist. This actively prevents a premature LH surge from the pituitary gland.
By blocking the brain’s signals to the ovaries, the GnRH medications halt the natural hormonal cascade that would lead to a spontaneous menstrual period or ovulation. This controlled state allows the medical team to maximize the number of mature eggs retrieved on a precise schedule.
What Happens Immediately After Egg Retrieval
Following the 10 to 14 days of stimulation, the mature eggs are retrieved in a minor outpatient procedure. Immediately after the retrieval, all hormonal stimulation medications are stopped, which is the direct trigger for the first post-procedure bleeding event. The ovaries, which were producing high levels of estrogen due to the numerous stimulated follicles, rapidly cease this hormone production.
This sudden and steep decline in circulating estrogen and progesterone levels creates a hormonal crash. The uterine lining, which thickened considerably under the influence of the high estrogen during the stimulation phase, is no longer supported by these hormones. This hormonal withdrawal signals the endometrium to shed, resulting in a withdrawal bleed.
This initial bleeding is not considered a true menstrual period, as a normal period follows the collapse of the corpus luteum after a failed ovulation. The withdrawal bleed generally begins within five to ten days after the egg retrieval procedure.
The characteristics of this first bleed can be noticeably different from a regular period. Some individuals report a heavier flow due to the significant thickening of the uterine lining. Others may experience a lighter flow or more intense cramping.
Impact on Menstrual Regularity and Menopause
Concerns that egg freezing might cause premature menopause or permanently disrupt the menstrual cycle are not supported by scientific evidence. The procedure is designed to only collect the eggs that were recruited for growth in that specific cycle and were already destined to die off in a process called atresia. By stimulating this cohort of eggs, the process utilizes eggs that would have been lost anyway, rather than depleting the overall ovarian reserve.
Therefore, the vast reserve of dormant eggs within the ovaries remains untouched by the stimulation and retrieval. Egg freezing does not accelerate the natural timeline toward menopause, which is determined by a person’s genetics and the total number of eggs they were born with.
The menstrual cycle typically returns to its normal rhythm and regularity shortly after the first withdrawal bleed. Most individuals find their cycle is fully back to its baseline pattern within one to two cycles following the retrieval.