For a trigger shot in an IVF cycle, 30 or more mature follicles are generally considered too many, as they significantly increase the risk of severe ovarian hyperstimulation syndrome (OHSS).
When a patient develops 30 or more mature follicles, fertility specialists may choose to cancel the trigger shot and, consequently, the entire IVF cycle. This decision is made to prioritize the patient's safety and prevent severe OHSS, a potentially serious complication.
Why Too Many Follicles Are a Concern
While the goal of ovarian stimulation in IVF is to produce multiple mature eggs, an excessive number can lead to complications. The primary concern with a high follicle count is the risk of Ovarian Hyperstimulation Syndrome (OHSS).
OHSS is a condition where the ovaries become swollen and painful, and fluid leaks into the abdomen and, in severe cases, other parts of the body. Symptoms can range from mild bloating and discomfort to severe issues like:
- Severe abdominal pain
- Rapid weight gain
- Vomiting and diarrhea
- Shortness of breath
- Reduced urination
- Blood clots
- Kidney failure (rare)
The trigger shot, which typically contains human chorionic gonadotropin (hCG), is known to exacerbate OHSS. hCG plays a crucial role in the final maturation of eggs and triggering ovulation, but it also increases the permeability of blood vessels, leading to fluid shifts characteristic of OHSS.
Managing the Risk of OHSS
Fertility specialists carefully monitor follicle development during IVF cycles to mitigate the risk of OHSS. This involves:
- Regular Ultrasound Scans: To count and measure follicle size.
- Blood Tests: To monitor estrogen levels, which rise with the number of developing follicles.
- Adjusting Medication Dosages: Stimulating hormones may be reduced if the ovarian response is too robust.
Strategies to Prevent Severe OHSS:
When the risk of OHSS is high due to a large number of follicles (e.g., 30 or more), several strategies might be considered:
- Canceling the Trigger Shot: This is a crucial step to prevent severe OHSS if the risk is deemed too high.
- "Coast" the Cycle: Reducing or stopping stimulation medication for a day or two to allow estrogen levels to drop before administering the trigger.
- Utilizing GnRH Agonist Trigger: In some cases, a GnRH agonist can be used as a trigger instead of hCG. This type of trigger significantly reduces the risk of OHSS, though it may require a "freeze-all" approach for embryos, meaning all embryos are frozen for transfer in a subsequent cycle, rather than a fresh transfer.
- Elective Freeze-All: If a trigger shot is administered despite a high risk, or if the response is still considered high, all resulting embryos may be frozen for transfer in a later cycle. This avoids the hormonal surge associated with pregnancy, which can worsen OHSS.
The decision to cancel a trigger shot or implement other strategies is always made by the fertility specialist based on the individual patient's response and risk assessment. The goal is to maximize the chances of a successful pregnancy while ensuring the patient's safety.
For more information on OHSS and its management, you can refer to resources from organizations like the American Society for Reproductive Medicine (ASRM).
