The effects on ovarian activity of delaying versus immediately restarting combined oral contraception after missing three pills and taking ulipristal acetate 30 mg.

Objective: Among combined oral contraception (COC) users, to determine the effect on ovarian activity and ovulation of waiting five days before restarting COC, versus restarting immediately, having taken ulipristal acetate 30 mg (UPA, the dose used for emergency contraception) after missing three consecutive COC pills.

Study Design: Women already using COC were enrolled for two cycles of COC use (21/7 regimen). In cycle 2, all women omitted COC pills for three consecutive days (days 5,6,7), and on day 8 took UPA 30 mg. They were randomized either to restart their COC pills that same day (immediate restart) or to wait five days (delayed restart). Transvaginal ultrasound, and blood sampling for estradiol and progesterone were undertaken on days 4,8,11,13,15,18,22 and 26. A modified Hoogland score was used to quantify ovarian activity/ovulation and to assess whether luteal phase progesterone concentrations were sufficiently 'adequate' to have conferred a theoretical risk of pregnancy.

Results: No one ovulated with risk of pregnancy during the five days following UPA. Among 26 women with immediate restart, none ovulated with a theoretical risk of pregnancy at any time in the cycle. Four of 23 women (17.4% CI [5.0; 38.8]) with delayed restart ovulated with theoretical risk of pregnancy before the end of the cycle. This difference was statistically significant (p = 0.042).

Conclusion: Women who delay restarting COC for five days after taking UPA 30 mg are at much greater risk of ovulation, and therefore theoretically of pregnancy, than if they restart their COC on the same day as taking UPA. Current recommendations should be revisited.

Implications: Women who take UPA-EC after having missed combined oral contraceptive pills are advised to wait five days before restarting the COC. This delay puts them at risk of ovulation and, if intercourse occurs, theoretically therefore of pregnancy. Women who restart their COC pills immediately are much less likely to ovulate. The label for UPA-EC and clinical guidelines on using EC after missed pills should be revisited.