one , three , and four pregnancies occurred during treatment with norethisterone acetate 0.3 mg. , norgestrel 0.05 mg. , and chlormadinone 0.5 mg. , respectively , corresponding to pregnancy rates of 4 , 9 , and 12 per 100 woman-years of use.all three effective progestogens were very much less acceptable than modern low-dose combined oral contraceptives .
C0032961
pregnancies
C0068980
norethisterone