Inhibition of follicular growth by two different oral contraceptives (monophasic and triphasic) containing ethinylestradiol and gestodene.

OBJECTIVE

To evaluate the inhibition level of ovarian follicular growth produced by a triphasic oral contraceptive (OC) containing ethinylestradiol and gestodene vs. the level produced by a monophasic OC containing the same components.

METHODS

A randomized, blind, cross-over trial was performed in a sample of 56 women. The follicular diameters were measured in 56 cycles under triphasic contraceptive treatment, and the other 56 under monophasic contraceptive treatment, using vaginal ultrasound. The statistical analysis was performed using the Student's t test.

RESULTS

The mean follicular diameter under monophasic OC treatment was found to be 8.16 mm (standard deviation 4.5), and while under triphasic OC treatment was found to be 7.44 mm (standard deviation 2.8) (p > 0.05). In 17 out of 112 cycles (15%), a certain degree of follicular activity was found (follicular diameter more than 10 mm), 10 cycles under monophasic OC and 7 cycles under triphasic OC.

CONCLUSIONS

The triphasic OC provides good inhibition of follicular growth and excellent contraceptive efficacy.