In Vitro Fertilization (IVF) treatment requires precise timing and consistent administration of hormone-based medications to successfully guide the reproductive cycle. These medications control ovarian function, promote the growth of multiple eggs, and prepare the uterine lining for embryo implantation. While medication adherence is a factor in optimizing outcomes, a single missed dose does not automatically lead to cycle failure. The resulting impact depends heavily on the specific medication, the stage of the cycle, and the time elapsed since the scheduled injection.
Immediate Steps Following a Missed Injection
The first and most important response upon recognizing a missed injection is to remain calm. Immediately note the exact time the injection was supposed to be administered and the current time of realization.
The next step is to contact the fertility clinic or the on-call physician immediately, regardless of the time of day. Fertility clinics have established protocols tailored to the patient’s specific treatment plan and bloodwork. Patients must never attempt to self-adjust the dosage or administer a double dose without explicit instruction from their medical team.
If the missed dose is for a medication other than the trigger shot and only a short time has passed, the clinic may advise taking the dose immediately. If the delay is significant, the instruction may be to simply skip the missed dose and resume the normal schedule, or the physician may introduce a revised schedule. Following the clinic’s direction precisely is the only way to mitigate the potential consequences to the cycle.
Impact of Missed Doses Based on Injection Type
Stimulation Medications (Gonadotropins)
Stimulation medications (gonadotropins), such as Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH), encourage multiple ovarian follicles to grow synchronously. Missing a dose of these daily injections disrupts the consistent hormonal environment necessary for optimal follicle development. The consequence of a missed dose is generally less severe if it occurs early in the stimulation phase.
If a dose is missed later in the stimulation phase, it can lead to uneven growth among the cohort of developing follicles. This disparity may result in some eggs reaching maturity while others remain too small for retrieval, reducing the total egg yield. Missing a dose of a GnRH-antagonist, which prevents premature ovulation, is particularly concerning. A significant delay risks an unscheduled Luteinizing Hormone (LH) surge, causing the eggs to be released before the scheduled retrieval.
The Trigger Shot (hCG or GnRH Agonist)
The trigger shot (hCG or GnRH agonist) is the most time-sensitive injection in the entire IVF cycle. This medication initiates the final maturation of the eggs and is timed precisely 34 to 37 hours before the egg retrieval procedure. Missing the trigger shot or delaying its administration by more than a very small window can have severe implications for the cycle.
If the trigger shot is missed, the eggs may not undergo the final maturation necessary for successful fertilization. This can lead to the retrieval of immature eggs that are not viable. Alternatively, a significant delay can result in premature ovulation, where the eggs are released before the retrieval can take place. In either scenario, the cycle may result in no retrievable eggs, potentially leading to cycle cancellation.
Progesterone/Luteal Support
Progesterone is a hormone administered after egg retrieval or before a frozen embryo transfer (FET) to prepare and support the uterine lining for embryo implantation. This luteal phase support maintains a receptive endometrium and is often continued through the first few weeks of pregnancy. Missing a single dose of progesterone is less likely to cause immediate cycle failure compared to missing the trigger shot.
In a fresh embryo transfer cycle, the ovaries, having been stimulated, may still produce some endogenous progesterone, offering a small buffer against a missed dose. However, in a fully medicated FET cycle, the ovaries are suppressed, and the patient is entirely dependent on the exogenous progesterone for uterine lining support. Repeatedly missing doses, especially in a medicated FET cycle, can cause the uterine lining to destabilize, potentially compromising implantation or early pregnancy maintenance.
Clinical Assessment and Protocol Adjustments
When a missed dose is reported, the fertility clinic initiates a rapid, specific assessment to determine the best course of action. The decision-making process is based on three factors: the function of the drug, the stage of the cycle, and the time elapsed since the scheduled injection. For most daily stimulation or luteal support medications, the physician may advise an immediate catch-up dose or a minor adjustment to subsequent dosing times.
In cases involving a significant delay or a highly sensitive drug like the trigger shot, the clinic may perform emergency blood tests to check current hormone levels. Measuring estradiol or progesterone levels can help determine the current hormonal status and assess the risk of premature ovulation. Based on these results, the physician may decide to slightly delay the egg retrieval by a few hours to allow for adequate egg maturation.
Fertility clinics are accustomed to managing these occurrences, as patients are often juggling complex schedules and high-stakes treatments. The medical team’s primary goal is to salvage the cycle with minimal impact on the outcome. While a missed injection requires immediate attention, established mitigation protocols provide a safety net.