Empty Follicle Syndrome: What Happened and What Comes Next

What "empty" actually means

During stimulation, ultrasound measures follicles, the fluid-filled sacs where eggs mature. A follicle is visible on ultrasound. An egg isn't. Before retrieval you get a trigger shot, usually hCG, a GnRH agonist, or both, that tells the eggs to complete maturation and loosen from the follicle wall so they can be aspirated.

It's normal to retrieve fewer eggs than the number of follicles counted. Some follicles are small, some eggs aren't collected, and some follicles simply don't contain a retrievable egg. That alone isn't EFS. A 2017 review in Reproductive BioMedicine Online (Revelli and colleagues) defines empty follicle syndrome as the complete failure to retrieve oocytes after ovarian stimulation, despite apparently normal follicle development and hormone production.

The same review describes the two forms in the quick answer:

How rare is it?

Estimates depend on how strictly EFS is defined. The largest recent dataset we found is a 2024 retrospective study in Frontiers in Endocrinology by Luo, Xu, and Hao. It covered 21,567 retrieval cycles in 14,066 patients at one Chinese hospital between 2016 and 2020. Using strict criteria, they identified EFS in 54 patients, or 0.38%. The authors note that earlier estimates using strict definitions ranged from 0.045% to 0.59%.

So if this happened to you, you're in a small group. That can feel isolating. It also means your clinic will probably want to investigate the cycle carefully rather than assume it will happen again.

Why it happens

Trigger problems (false EFS)

Revelli's review identifies an error in hCG administration as the cause of false EFS. In real life that can look like:

• Injecting at the wrong time, including time-zone mix-ups when traveling for treatment
• Using the wrong medication or the wrong dose, or not mixing a powdered medication correctly
• An injection that didn't fully deliver, such as a misfired pen, leaking syringe, or wrong technique
• Medication that was stored incorrectly or had expired

In the Luo study, only one of the 54 cases was clearly an injection error. That patient was the only one with a negative urine hCG on the day. The authors tentatively attributed most of the remaining cases (51) to an inadequate ovarian response to hCG, and two to problems with egg development.

Factors that raise the risk

In that same cohort, polycystic ovary syndrome was an independent risk factor. People with PCOS had about 2.7 times the adjusted odds of EFS, and PCOS was present in 45.1% of EFS cases versus 18.6% of other patients. That doesn't mean EFS is likely with PCOS. It's still rare. But it's a reasonable thing to raise when planning your trigger.

Rare biological causes (genuine EFS)

For genuine EFS, the cause often isn't found. Researchers have reported variants in genes involved in the hCG/LH receptor and in the zona pellucida, the egg's outer shell, in some families and case reports. These are rare. Genetic testing is usually considered only when EFS repeats or there is a strong family pattern.

What clinics can do on retrieval day

Many clinics take steps to catch trigger problems early:

• Checking the trigger worked. Some clinics measure hCG, or LH and progesterone after an agonist trigger, the morning after the trigger shot. A low result can prompt a repeat trigger before retrieval.
• Stopping after the first ovary. If the first ovary yields no eggs, the doctor may pause, check blood hCG, and, if it's low, give another trigger and attempt the second ovary later. In the Luo cohort, the timing of a second "rescue" retrieval attempt appeared to affect whether eggs were obtained, but those subgroups were small and the data were retrospective.

If none of this happened in your cycle, it's reasonable to ask whether your clinic does it routinely. It doesn't mean anyone did anything wrong.

What it means for your next cycle

This is the part most people most need to hear. In the Luo study, 15 patients with EFS who didn't have a baby from that cycle went on to another cycle. In the next cycle:

Luo Z, Xu S, Hao G. Front Endocrinol 2024. Single centre, retrospective, small subgroup. Average eggs retrieved were also higher in the next cycle (10.5 vs 3.7 as reported).

The authors concluded that a single episode of EFS doesn't necessarily mean declining fertility. It's a small group from one centre, so it can't predict your individual chances. It's still a meaningful counterweight to the fear that EFS means your eggs are "gone."

Changes doctors commonly consider for the next cycle include re-teaching trigger technique, changing the type or brand of trigger, double-checking timing in writing, adding a blood check after the trigger, and sometimes using a different trigger approach. ESHRE's 2025 ovarian stimulation guideline says the evidence on dual triggers (hCG plus a GnRH agonist) is too limited to draw firm conclusions for general IVF populations. After a documented EFS, your doctor may weigh it differently, and that's a reasonable individualized decision.

A trigger-shot checklist for next time

• Get the exact trigger time in writing, with the time zone stated. Set two alarms.
• Confirm the medication name and dose against the written instructions before injecting. If anything looks different from what you were told, call before injecting, not after.
• If the medication needs mixing, ask for a demonstration or a video from your clinic.
• Check the expiry date and storage instructions when you pick it up.
• Photograph the empty syringe or pen and note the exact time. That helps the clinic troubleshoot if anything goes wrong.
• Ask whether the clinic will check a blood level the morning after the trigger.

If you're traveling abroad for IVF, time zones deserve extra care. Agree with the clinic in writing which local time the trigger is due. colombianivf.com has information for people considering IVF in Colombia, and the same time-zone discipline applies wherever you go.

If it happens more than once

Repeated EFS is rare, and it's taken more seriously. In the Luo cohort, two patients had repeated EFS. In both, only immature eggs with an abnormal zona pellucida were found. Neither had a family history of infertility, and both declined genetic testing. Revelli's review describes the best treatment and prognosis for genuine EFS as still poorly understood.

If EFS repeats, it's reasonable to ask about:

• A detailed review of both cycles: trigger timing, blood levels, what the embryologist saw in the follicular fluid, and whether any immature eggs were found
• Genetic evaluation, if your doctor thinks it's warranted
• A second opinion at a centre with experience in rare egg-maturation problems
• Whether in vitro maturation (IVM) or other approaches are being studied for your situation
• Donor eggs, if your own eggs repeatedly can't be retrieved or matured

Retrieval problems sit on a spectrum with low or failed fertilization. If you get some eggs but they don't fertilize, that's a different problem with different tests.

Questions for your doctor

• Do you think this was false or genuine EFS? Was my hCG level checked on retrieval day?
• Were any eggs, mature or immature, seen in any follicle?
• What will you change about my trigger next time: type, timing, dose, or a blood check?
• Does my PCOS or my response pattern change your plan?
• Would you recommend any genetic testing, now or only if it happens again?
• Does the clinic have any policy on charges for a cycle with no eggs retrieved?

Frequently asked questions

Sources