In an open, randomized study in an outpatient clinic of a large teachi
ng hospital, thirty-one female volunteers with regular cycles and esta
blished ovulation by ultrasonography were given one of two triphasic o
ral contraceptives containing ethinylestradiol combined with levonorge
strel or desogestrel during six cycles og treatment. The main outcome
measures were transvaginal ultrasonography and serum E(2) and P measur
ements in pill cycles 1, 3 and 6. No ovarian activity was found in 10
subjects. Among the remaining 21 women who showed ovarian activity, mo
st follicle-like structures developed in the pill-free week and decrea
sed in size or disappeared in the first pill week. One women taking tr
iphasic desogestrel had evidence of a luteinized unruptured follicle a
nd one women taking triphasic levonorgestrel had a possible ovulation.
The latter women also showed symptoms of lower abdominal pain. A stat
istically significant difference in ovarian activity between the two o
ral contraceptives could not be established. The two triphasic oral co
ntraceptives suppressed ovarian activity to the same degree. A trend w
as seen towards increasing ovarian activity with duration of use in bo
th treatment groups.