[Residual function in the ovary during low-dose oral contraceptive treatment].

Development in oral contraceptives during the past 20 years has involved continued reduction in the total quantity of hormone and alterations in the oestrogen/gestagen ratio and in the steroid structure for the gestagens employed. These changes have been undertaken primarily to counteract metabolic side effects and influence on the haemostatic system. Inhibition of the mechanism of ovulation is, however, also dependent on the steroid dosage and in cases where low-dosage oral contraception is employed, ultrasound investigations have demonstrated a risk of continued ripening of follicles during treatment. Correspondingly, hormone measurements during the pill-free week have demonstrated increase in the follicle-stimulating hormone, luteinizing hormone and the oestrogen concentration. The permissible margin of error in employing oral contraception has therefore diminished and is more dependent on the dosage and potency, particularly of gestagens. As the critical phase for failure of treatment is the first week of intake of oral contraceptives, it is important that treatment is commenced at the correct time not only at the commencement of treatment but also after the pill-free periods. If a pill is forgotten during the preovulatory oestrogen level and two pills are then taken, this may be interpreted by the organism as a positive oestrogen feed-back and, theoretically, this may result in increased gonadotropin production and thus further increase the risk of ovulation. In cases with the risk of malabsorption on account of gastro-intestinal disease and in cases with interaction with other medicaments, employment of alternative forms of contraception is recommended.(ABSTRACT TRUNCATED AT 250 WORDS)