Does a Trigger Shot Increase Your Chances of Getting Pregnant?

A trigger shot does not raise your odds of pregnancy on its own. What it reliably does is control when ovulation happens, so your care team can time a procedure with precision instead of guessing. This article covers what the evidence actually shows about trigger shots and pregnancy rates, and where a number simply does not exist to give.

What Is a Trigger Shot and How Does It Work?

A trigger shot is an injection of hCG or a GnRH agonist that imitates the natural luteinizing hormone surge, prompting eggs to complete maturation and be released. Hourly ultrasound monitoring puts the average interval to follicle rupture at 38.3 hours, with an observed range of roughly 34 to 46 hours.

A trigger shot is a hormone injection, typically hCG (human chorionic gonadotropin) or a GnRH agonist, that mimics the natural luteinizing hormone (LH) surge produced before ovulation. Once given, it signals the ovaries to finish maturing the eggs and release them, the last step in the ovulation sequence rather than a separate treatment.

In a natural cycle your brain releases LH on its own; in treatment, the trigger shot lets your team choose that moment, so ovulation happens about 38 hours later, usually somewhere between 34 and 46 hours, instead of on an unpredictable schedule. That is what makes it useful across three settings: timed intercourse, intrauterine insemination, and IVF retrieval.

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Does a Trigger Shot Increase Your Chances of Getting Pregnant?

A trigger shot does not set your odds of pregnancy on its own; the treatment and your age do. It fixes when ovulation happens, on average about 38 hours later. Against unmonitored timing that adds real precision, but a 2023 meta-analysis found no significant difference versus careful LH monitoring.

Here is the honest, evidence-based answer, in four parts.

First, the trigger reliably induces final maturation and release of the egg. That part of its job is well established.

Second, its real function is control and predictability over when ovulation happens, not an increase in the underlying chance an egg fertilizes or implants.

Third, against careful monitoring of the natural LH surge, the evidence does not show a trigger shot improves pregnancy rates. A 2023 meta-analysis in Obstetrics and Gynecology, thirteen studies, found no significant difference between hCG triggering and endogenous LH monitoring (OR 0.92, 95% CI 0.69 to 1.22, P=.53). ASRM’s 2020 unexplained infertility guideline reports a similar pattern. That comparison is against careful monitoring; against unmonitored timing, the trigger adds real precision. Both are true at once.

Fourth, none of this diminishes the trigger shot’s value. It lets a procedure be scheduled exactly and prevents cycles lost to a missed LH surge, a different claim from “raising your chances,” but a real one.

So what actually sets your odds? Treatment type and your age, not the trigger shot itself. If you are looking for a single number attached to “trigger shot,” that number does not exist.

How It Compares to Tracking Your Natural LH Surge

For pregnancy rates, careful LH surge tracking and a trigger shot perform similarly. A 2023 meta-analysis in Obstetrics and Gynecology comparing the two across thirteen studies found no significant difference, and ASRM’s 2020 unexplained infertility guideline reports the same finding. The trigger’s advantage is scheduling certainty.

If you are wondering whether tracking your own LH surge with ovulation kits works just as well, the pregnancy-rate evidence says yes, when tracking is careful and consistent. Where a trigger shot pulls ahead is scheduling certainty, not a higher biological chance of success. A 2025 update to Cochrane review CD006942, on IUI synchronization specifically, found evidence between methods insufficient, low certainty. That applies to IUI, not IVF or comparisons between trigger types.

How the Trigger Shot Fits into an IVF Cycle

In IVF the trigger sets the timing of egg retrieval. On outcomes, a 2021 meta-analysis of randomized trials in Reproductive Biology and Endocrinology found a higher live birth rate with a dual trigger of GnRH agonist plus hCG than with hCG alone, at moderate certainty across 1,048 participants.

In IVF, the trigger shot’s job is narrower: it sets the exact timing of egg retrieval, a fixed interval afterward, which is why it is a required step, not an optional add-on.

Where trigger choice does affect IVF outcomes is hCG alone versus a dual trigger (a GnRH agonist plus hCG). A 2021 meta-analysis of randomized trials in Reproductive Biology and Endocrinology, 1,048 participants, moderate certainty, found a higher live birth rate with the dual trigger.

Ovidrel, Pregnyl, Lupron and Dual Trigger: What the Options Are

Ovidrel and Pregnyl are hCG triggers and remain the standard option. A GnRH agonist such as Lupron is chosen mainly to reduce ovarian hyperstimulation risk. A 2021 meta-analysis of randomized trials found a dual trigger combining both produced a higher live birth rate than hCG alone, at moderate certainty.

A patient’s history shapes which option makes sense. A history of severe OHSS shifts the conversation toward a GnRH agonist trigger, lower OHSS risk than hCG. A premature LH surge can also change the protocol, sometimes calling for a GnRH antagonist approach with adjusted timing.

How to Know If Your Trigger Shot Worked

Symptoms do not tell you whether a trigger shot worked. Product labeling points to a rise in serum progesterone as the marker of ovulation, which is why clinics schedule a blood test rather than ask how you feel. Home ovulation tests are unreliable afterward, because injected hCG cross-reacts with them.

It is a fair worry, and symptoms will not answer it. Serum progesterone, measured with a blood test, is the marker your clinic relies on, not bloating, cramping, or how you feel. Home ovulation tests are unreliable afterward, since injected hCG cross-reacts and can mislead. Ask your team when your progesterone check is scheduled.

If Something Goes Wrong: Missed Timing and Empty Follicle Syndrome

Empty follicle syndrome, where no eggs are retrieved despite an apparently correct trigger, is uncommon. A 2026 review reports a prevalence of 0.2% to 7%, and notes that estimates vary widely with the definition used. Reviews distinguish a false form, linked to inadequate trigger exposure, from a genuine form.

If you think you missed a dose, took it at the wrong time, or are unsure it went in correctly, call your clinic first. Cycles built around a trigger shot are usually adjustable.

Empty follicle syndrome, no eggs retrieved despite an apparently correct trigger, is uncommon. A 2026 review reports a prevalence of 0.2% to 7%, wide because estimates vary with the definition used. Reviews distinguish a false form, linked to inadequate trigger exposure and often preventable by adjusting the protocol, from a rarer, less understood genuine form. A retrieval with no eggs is not the whole story for how many retrievals a path to a baby typically takes.

Speak with our international patient coordinator about how a cycle would be scheduled around your travel.