Follicle Monitoring

Definition - What does Follicle Monitoring mean?

Follicle monitoring is an ultrasound-guided monitoring of the size and number of the ovarian follicles. It is performed in women receiving fertility treatments to determine the quality, quantity, and development of eggs contained in the follicles and hence, determine the response to treatment. The ultrasound employed for follicle monitoring also helps in assessing the thickness of the uterine lining. Measuring the estradiol (estrogen), which is produced by mature follicles further facilitates follicle monitoring. The greater the estradiol concentration, the greater is the number of mature follicles.

FertilitySmarts explains Follicle Monitoring

Transvaginal ultrasound is done around day 3 of the IVF or fertility treatment cycle to measure the baseline size of the follicle as well as assess the follicular count. Around day 7 of the procedure, one of the several follicles is expected to outgrow others and contain a mature egg that is destined to be released after the follicle bursts during ovulation. This dominant follicle is round in shape, has smooth borders, and is about 10 mm in size by days 5 to 7 of the menstrual cycle. The rest of the follicles degenerate and die.

The ovaries and uterus communicate with each other to attain the goal of successful reproduction. Estrogen produced by the ovarian follicles during the follicular phase of the menstrual cycle also serves to stimulate the inner uterine lining. A thickened uterine lining (as seen on the ultrasound) allows for implantation of a fertilized egg.

Once the dominant follicle approaches an ideal size of 16 to 20 mm, along with the rising estrogen levels and thickened uterine lining, Hcg or Lupron, also known as a "trigger shot," is administered to trigger the ovulation. Follicle monitoring is then done daily to determine the onset of ovulation.

Following changes (as determined by ultrasound) in the dominant follicle signal the beginning of ovulation.

  • The follicle will reduce in size or suddenly disappear
  • The follicle no longer has a smooth outline
  • The follicle appears brighter on an ultrasound

Follicle tracking helps to determine the count and ripeness of follicles, allowing for a safe induction of ovulation. By predicting the best timing for ovulation and quantity of eggs that will ovulate, follicle monitoring may assist in predicting the success of fertility treatment.

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