Follicle monitoring: what is measured, when, and how to track it
Follicle monitoring is the backbone of any fertility treatment cycle — natural, IUI or IVF. At each visit the follicles in your ovaries are measured, the lining of the uterus is checked, and blood tests are often taken. This page brings together what is actually measured, how often, and how to keep all the numbers in one place so you can see a trend rather than a single data point.
What follicle monitoring measures
A follicle is a fluid-filled sac in the ovary containing a developing egg. A transvaginal ultrasound counts the follicles in each ovary and measures their diameter in millimetres. Your doctor watches the growth rate — often around 1-2 mm per day during the active phase — and uses it to adjust medication doses and set the next visit.
- • Number of follicles in the right and left ovary
- • Diameter of each significant follicle (mm)
- • Endometrial (uterine lining) thickness and pattern
- • Accompanying blood tests: estradiol (E2), LH, progesterone
When the scans usually happen
The schedule varies between clinics and between patients, but the overall shape is similar. The exact frequency is always set by your medical team based on how you respond to medication.
| Stage | Typical timing | What is checked |
|---|---|---|
| Baseline scan | Cycle day 2-3 | Resting ovaries, cysts, thin lining |
| First monitoring scan | Day 6-8 | Early growth, dose adjustment |
| Follow-up scans | Every 1-3 days | Follicle sizes, lining, E2 |
| Approaching ovulation / retrieval | Lead follicle around 17-22 mm | Timing of trigger shot or retrieval |
How to track results across the cycle
A single value says little; the trend is what matters. After each visit, record the date, cycle day, the number and size of follicles in each ovary, endometrial thickness and blood results — and keep the visit summary or form next to the numbers.
- 1. Write down the date and cycle day for every scan.
- 2. Record follicles per ovary, e.g. "Right: 14, 12, 9 / Left: 15, 11".
- 3. Add endometrial thickness and that day's blood results.
- 4. Save the visit summary or a photo of the form with the measurement.
- 5. Arrive at the next visit with previous numbers in front of you to ask focused questions.
Track your monitoring in Ovylia
Ovylia has a monitoring page for follicle scans, endometrial thickness and blood tests, PDF upload for visit summaries, plus medications, appointments and reminders — all in English and Hebrew.
Start tracking your monitoringFrequently asked questions
What is follicle monitoring?
Follicle monitoring is a series of transvaginal ultrasound scans (usually alongside blood tests) that count the follicles in each ovary and measure their diameter in millimetres, so your team can see how they develop across the cycle or treatment.
When does follicle monitoring start?
A baseline scan is typically done on day 2-3 of the cycle, with follow-up scans every two to three days from around day 6-8, and sometimes daily close to ovulation or egg retrieval. Your clinic sets the exact schedule based on how you respond to medication.
What follicle size is considered mature?
A follicle is generally considered mature around 17-22 mm, but the timing of the trigger shot or retrieval depends on a combination of follicle size and count, endometrial thickness and hormone levels — and is always decided by your medical team.
What else is checked at the same visit?
The same appointment usually measures endometrial (uterine lining) thickness and pattern, and often includes blood tests for estradiol (E2), LH and progesterone. Together they give a fuller picture of the cycle.
This page is general information and not medical advice. Values and scan frequencies vary between patients and clinics — every decision about treatment, dosing or timing is made by your treating physician.