Approximately one-third of women use combined oral contraceptives for birth control. These hormonal preparations contain both estrogen and progestin components. Oral contraceptives suppress the hypothalamic-pituitary-ovarian axis, leading to the suppression of gonadotropins LH and FSH. As a result, follicle maturation (egg development) is inhibited, and ovulation (egg release) is suppressed.

The safety of contraception is measured using the Pearl Index. If 100 women use the same contraceptive for one year and one pregnancy occurs during this time, the Pearl Index is 1. For birth control pills, the Pearl Index ranges between 0.1-0.9, meaning 1 to 9 pregnancies per 1,000 women who take the pill for a year. In most birth control pills, the progestin dose is sufficient for contraception. Estrogen is required for cycle control and its effects on the endometrium (uterine lining).

Administration

• Pills are usually taken for 21 days. During the subsequent pill-free interval, a withdrawal bleed occurs.
• Most pills contain ethinylestradiol as the estrogen component, with only a few containing estradiol or estradiol valerate.
• Since 2021, estetrol has been available, which acts strongly on the uterus but has minimal effects on the breast and liver. This should reduce side effects like water retention. However, the thrombosis risk is still unknown due to limited data.

Missed Pill – What to Do?

• Missed Pill (within 24 hours): Take the missed pill as soon as possible and continue as usual.
• First Week – One or More Missed Pills: Take the last missed pill as soon as possible, then continue as usual. Use additional contraception for the next seven days. If unprotected intercourse occurred, consider emergency contraception (morning-after pill).
• Second/Third Week – One to Two Missed Pills: Take the last missed pill and continue as usual. Skip the hormone-free interval and immediately start the next pill pack.
• Second/Third Week – Three or More Missed Pills: Take the last missed pill, skip the hormone-free interval, and use additional contraception for seven days. Emergency contraception may be needed if unprotected intercourse occurred.

Emergency Contraception (Morning-After Pill)

In case of contraceptive failure, postcoital pills are available:

1. Levonorgestrel: Should be taken as early as possible, but no later than 72 hours after intercourse, reducing pregnancy risk by 75-85%.
2. Ulipristal Acetate: Can be taken up to 120 hours after intercourse.
3. Copper IUD: As an alternative, a copper intrauterine device can be inserted within five days, providing both emergency contraception and long-term protection (pregnancy rate < 0.2%).