Background: Accurate prediction of ovulation is important in the management of female infertility.
Aim: To determine the sonographic sensitivity of reduction in follicular size and disappearance of ovarian follicle as predictors of imminent ovulation.
Methods: This was a longitudinal study involving 100 women between the ages of 18 and 35 years. Transvaginal sonography with 6.5 MHz probe frequency was performed with a General Electric (RT 2800) ultrasound machine. Dominant follicles were identified and measured in both the longitudinal and transverse planes and their disappearance was monitored prior to ovulation. Laboratory luteinizing hormone test strips were used to test serum samples collected daily from each patient to confirm the time of ovulation.
Results: Pre-ovulation follicular size among the subjects was in the range of 18–36 mm while the mean follicular size was 26.78 ± 4.03 mm. Prior to ovulation, disappearance and reduction in follicular size was noted in 59% and 41% of subjects, respectively. Luteinizing hormone test was also positive and peaked prior to ovulation in 92% of the subjects among whom follicles disappeared in 37% while their size reduced in 55%. There was no statistically significant difference between sonographic and laboratory findings (p > 0.05). Age, height, weight and body mass index do not have significant influence (p > 0.05) on follicular size and ovulation.
Conclusion: Sonographic observation of complete disappearance of a dominant follicle and reduction in follicular size of surrogate follicles after follicular rupture appeared to be a reliable predictor of imminent ovulation.