Disturbances of Ovulation:15-25% of women attending fertility clinics have ovulatory disturbance and require induction of ovulation. There can be either an ovulation or infrequent ovulation. In both cases pregnancy can not be expected in the absence of ovulation.
Ovarian Function Evaluation: Important Considerations:
- There is no direct access and we have to rely on indirect evidence.
- While sperms are ejaculated out of the man’s body and can be directly examined, the ovum stays within the body of the wife and can not be directly visualized.
- The ovum is shed at certain unknown time and survives for only 18-36 hours.
- Tests for ovulation therefore can be done only on specific days.
- Frequent evaluations ( 3 to 5 observations in a cycle) have to be done during woman’s monthly cycle to record normal variations in the size of the follicle by TVS & hormone levels throughout the cycle to draw the proper conclusions. The results of these are compared with each other.
Both ovulation and the hormones production need to be evaluated. Ovulation which involves maturity and extrusion of ovum is best evaluated by TVS. Hormone provides indirect evidence of ovulation but not with certainty. They are assessed directly by their levels in blood, and indirectly by cervical mucus studies, basal body temperature records and histology of endometrium taken by curettage. Endometrium Patterns on TVS reflects the effects of type of ovarian hormones & thickness their amount in blood. Its shadow is measured from outside to outside at the widest point. It needs 2-5 observations at 2-3 days interval.
Ovulation is best observed by Transvaginal Sonography by the development of follicles and their collapse. Ovarian follicles and changes in uterine endometrium are observed.
- Follicular diameter is measured and growth of leading follicle observed at intervals.
- Follicles measuring 3-4 mm can normally be seen in ovaries on cycle day-3.
- Follicles develop at a linear rate of 1 mm/day until day 10 when a single follicle is dominant.
- The dominant follicle continues to develop @ 2-3 mm a day for 4-5 days reaching a diameter of 13-33 mm before rupture (ovulation).
- Afterwards collapsed follicle in the form of corpus luteum is seen.
If development and the rupture of the follicle are observed, it is concluded that the ovulation has taken place without seeing the ovum. At times mature follicle does not rupture. At others an immature follicle may rupture. In both situations ovulation does not occur properly.