An ovarian follicle ultrasound is a non-invasive imaging technique that uses sound waves to create detailed pictures of the ovaries. This specialized ultrasound focuses on visualizing ovarian follicles, which are small, fluid-filled sacs within the ovaries. The procedure assesses these structures in the female reproductive system.
What is an Ovarian Follicle Ultrasound?
An ovarian follicle is a small, fluid-filled sac located within the ovaries, each containing an immature egg, also known as an oocyte. These follicles secrete hormones that influence the menstrual cycle. Women are born with a large number of primordial follicles, with approximately 200,000 to 300,000 present at puberty.
An ovarian follicle ultrasound, often called follicular tracking or monitoring, employs high-frequency sound waves to generate images of these follicles inside the ovaries. The scan visualizes these structures to determine their number, size, and growth patterns throughout the menstrual cycle.
When is an Ovarian Follicle Ultrasound Performed?
Ovarian follicle ultrasounds are performed for various clinical reasons, particularly in fertility and reproductive health. It helps monitor ovulation for natural conception, pinpointing the exact time an egg is released. This allows for optimal timing of intercourse to increase pregnancy chances.
The ultrasound is also used during fertility treatments such as in vitro fertilization (IVF) and intrauterine insemination (IUI). During IVF, multiple scans assess how follicles respond to fertility medications, ensuring the correct dosage and determining the ideal moment for egg retrieval. For IUI, monitoring follicle growth helps time the insemination procedure precisely.
The scan aids in diagnosing and managing conditions like Polycystic Ovary Syndrome (PCOS), often characterized by 12 or more small follicles (2-9 mm) per ovary or increased ovarian volume. It can also help investigate causes of irregular periods or infertility by identifying issues such as low ovarian reserve. While ovarian reserve often involves other tests like Anti-Müllerian Hormone (AMH) blood tests, the ultrasound provides a visual count of antral follicles, which correlates with the number of remaining eggs.
The Ovarian Follicle Ultrasound Procedure
Preparation for an ovarian follicle ultrasound varies by scan type. For a transabdominal ultrasound, a full bladder is often required to help visualize the uterus and ovaries. For a transvaginal ultrasound, which provides clearer images, an empty bladder is preferred.
The procedure can be performed using two main approaches: transabdominal or transvaginal. During a transabdominal scan, a transducer is moved across the lower abdomen. For a transvaginal ultrasound, a small, lubricated probe is inserted into the vagina, typically about 2-3 inches. This closer proximity allows for more detailed imaging of the ovaries and follicles.
During the scan, which usually takes about 10-15 minutes, the patient lies on an examination table. The sonographer or doctor manipulates the probe to capture images. Patients may feel some pressure, but the procedure is generally not painful. The images are displayed on a screen, allowing the healthcare provider to measure and count the developing follicles and assess the thickness of the endometrial lining.
Interpreting Ovarian Follicle Ultrasound Results
Interpreting ovarian follicle ultrasound results involves assessing several parameters. The number of follicles observed, particularly the antral follicle count (AFC), estimates a woman’s ovarian reserve by indicating the number of resting follicles. A higher number of mature-sized follicles (10 or more) is considered a good response, while fewer than three may suggest low ovarian reserve.
The size and growth rate of individual follicles are monitored. Follicles typically grow at a rate of 1-3 mm per day once they reach about 10 mm. A dominant follicle, most likely to release an egg, reaches a size between 16 and 22 mm before egg retrieval or ovulation. Follicles that are too small may indicate immature eggs needing more stimulation, while overly large follicles could suggest over-maturation or a risk of spontaneous ovulation.
Mature follicles indicate ovulation prediction. Once a follicle reaches its mature size, it is ready to release an egg. The ultrasound can also reveal issues such as the absence of follicles, which may point to primary ovarian insufficiency, or the presence of cysts, which are follicles larger than approximately 3 centimeters that did not rupture. The thickness of the endometrial lining is also measured; around 8 mm or greater by the day of the trigger shot is preferred for embryo implantation.