Follicular Monitoring of Ovary on Ultrasound | Ovulation & Fertility Tracking | Gynecological USG

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Follicular Monitoring of Ovary on Ultrasound | Ovulation & Fertility Tracking | Gynecological USG

Early Follicular Phase Day 1/2 - 0:00
Early Follicular Phase Day 3 - 4:36
Mid-Follicular Phase Day 7 - 6:10
Mid-Follicular Phase Day 9 - 8:42
Late Follicular Phase Day 11/12 - 9:16
Late Follicular Phase/Ovulation - 11:50
Ovulation/Luteal Phase - 12:26

Follicular monitoring through ultrasound is a crucial process used in reproductive medicine and gynecology to track the development of ovarian follicles.

Recruitment: A process in which a collection of follicles is formed. The dominant follicle is selected from this group later on in the cycle. These follicles usually measure 2-5 mm. Multiple small antral follicles are found in both ovaries.
Occurs during late luteal phase of previous menstrual cycle. The number of follicles may be between 3-12.

Follicular Selection: Occurs during day 1-5 of the cycle. Some follicles amongst the recruited ones which measure 5-10 mm are selected, whereas others regress and become atretic.

Baseline - Day 1-5
Purpose: To assess the ovary volume, follicular size, antral follicle count (AFC), and uterine endometrial thickness.
Check for:
Absence of cysts or large dominant follicles.
Measurement of baseline endometrial thickness.
Count and measure of antral follicles in both ovaries.
Follicle should not measure greater than 10 mm

Monitoring Follicular Development
Begin scans typically on Day 7-10 of the cycle.
Frequency of scans: Every 1-3 days depending on the ovarian response and follicular growth rate.
Follicle sizes are measured in millimeters using the largest dimension of the follicle.

Dominance: This process begins during Day 5-7 of the menstrual cycle. A follicle that measures 10 mm or more gets selected to be the dominant follicle. Other follicles begin to suppress.

Follicle Growth Rate: 1-2 mm per day
Dominant follicle: Round, with smooth margins and hypoechoic
Atretic Follicle: Small, irregularly shaped and may be echogenic
Daily monitoring is recommended once follicle measures greater than 16 mm.
Increased ovarian blood flow (with PSV greater 10 cm/s) is often observed during the mid-to-late follicular phase, particularly as the dominant follicle matures.
When the dominant follicle reaches 18-22 mm, it is considered mature.
At this stage, ovulation can be induced using medications like hCG or let the process proceed naturally (The day on which the follicle reaches 18–22 mm is variable).
Enhanced blood flow around the dominant follicle, indicates maturation and impending ovulation.
A follicle with strong peripheral vascularity is more likely to be viable and capable of releasing a healthy egg.
Power Doppler is used to assess follicle quality and select the optimal timing for interventions such as Ovulation induction and egg retrieval during IVF
The absence of vascularity or poor blood flow around a dominant follicle may suggest anovulation or follicular dysfunction.

Cumulus Oophorus: Small, hypoechoic structure with an echogenic border protruding into the antral fluid of the dominant follicle. It is seen at 12-14 days of the cycle.

Corpus Luteum:
The ruptured follicle becomes the corpus luteum after releasing the egg. It is seen around day 15-16.
Has thick irregular walls
Appears hypoechoic with some echogenic areas

Minimal anechoic free fluid in the cul de sac indicates ovulation has occurred.