An IVF cycle cancellation during the stimulation phase is a common and disappointing occurrence. This happens after the ovaries have been stimulated with injectable medications to develop multiple egg-containing sacs, or follicles, but the procedure is halted before the final egg retrieval. Understanding the reasons for cancellation and the biological consequences for the stimulated follicles helps clarify the path forward. The focus shifts from immediate egg collection to allowing the body to naturally reset its reproductive system.
Reasons an IVF Cycle is Stopped
The decision to cancel a cycle during the stimulation phase is made to protect the patient’s health or maximize the chance of success in a future attempt.
Poor Response
One frequent medical reason for cancellation is a poor ovarian response, where the ovaries produce too few follicles despite the medication. A cycle is stopped if fewer than three mature follicles are developing. Continuing the cycle in this scenario is often inefficient, as the likelihood of a successful egg retrieval and resulting pregnancy is significantly reduced.
Over-Response and OHSS Risk
Conversely, a cycle may be cancelled due to an over-response, putting the patient at high risk for Ovarian Hyperstimulation Syndrome (OHSS). This condition involves the ovaries becoming excessively swollen and can lead to fluid accumulation in the abdomen, posing health risks. Physicians monitor blood estradiol levels closely. If levels rise too high, or if an excessive number of small follicles develop, the cycle is stopped to prevent severe OHSS.
Premature Ovulation and Other Factors
A less common reason for cancellation is the risk of premature ovulation, monitored by checking luteinizing hormone (LH) and progesterone levels. If a natural LH surge occurs prematurely, the eggs may be released from the follicles before the scheduled retrieval, requiring the cycle to be abandoned. Non-medical factors also lead to cancellations, such as sudden patient illness, financial constraints, or critical issues at the laboratory.
The Biological Fate of Stimulated Follicles
When stimulation medications are abruptly stopped, the remaining follicles follow two primary biological processes: atresia and luteinization.
Atresia
Atresia is the body’s mechanism for follicular degeneration, where the unretrieved follicles are reabsorbed by the ovary and disappear. This regression is the most common path for small and medium-sized follicles that did not reach full maturity.
Luteinization and Cyst Formation
Larger, more mature follicles often undergo luteinization instead of atresia. Luteinization is the process where the follicle wall transforms into a corpus luteum, even without egg release. Because the follicle cells are highly stimulated, they begin to produce progesterone, forming a temporary, fluid-filled sac known as a functional cyst. These cysts are harmless and resolve on their own over the next few weeks or months.
Managing Ovulation Risk
The risk of spontaneous ovulation after a cancelled cycle is low, but possible if the patient was close to the trigger point or had a premature LH rise. To manage this risk and prevent painful cysts, the physician may administer a gonadotropin-releasing hormone (GnRH) antagonist or a short course of progesterone. This intervention helps “quiet” the ovaries, ensuring the remaining follicles safely regress or form benign, temporary cysts.
Timelines for Hormonal Recovery and Next Steps
After a cancelled stimulation cycle, the body needs time to clear the high levels of exogenous gonadotropins and reset the hypothalamic-pituitary-ovarian axis. The first sign of this reset is a withdrawal bleed, which acts as a period and occurs within two weeks of stopping the medications. The ovaries require additional time to return to a baseline state of quiescence.
Ovarian Clearance
Hormonal recovery and ovarian clearance range from four to eight weeks, depending on the extent of the stimulation. During this time, the body metabolizes excess hormones and functional cysts shrink. This delay is necessary because starting a new cycle while residual cysts are present can interfere with the development of a fresh cohort of follicles in the subsequent treatment.
Confirming Readiness
Before a new IVF cycle is approved, specific monitoring confirms the ovaries are ready. An ultrasound ensures any functional cysts have fully resolved and the ovaries are at their baseline size. Blood tests check that baseline hormone levels, such as estradiol, are appropriately low, confirming the body is no longer influenced by the previous stimulation. Once ovarian quiescence is confirmed, the physician can proceed with planning the next treatment protocol.