Oral Hormonal Contraceptives

The oral contraceptives in general use are synthetic steroids similar to the natural female sex hormones - the estrogens and progestins. These steroids are used in doses and in combinations that provide contraception by inhibiting ovulation.

When first developed, the 2 principal regimens of oral contraception were combined and sequential. In the combined method, pills containing estrogen and progestin are taken each day for 20-21 days. The sequential method, in which an estrogen pill is taken each day for 15-16 days followed by an estrogen-progestin pill each day for 5 days, has been abandoned in the U.S. because several studies showed a higher than normal incidence of endometrial cancer in women using this method of contraception.

The combined regimen is begun either with the onset of the menstrual cycle or on the Sunday closest to the start of menses. Since most oral contraceptive preparations are packaged in 28-day regimens (the pills taken the last 7 days being placebos), the Sunday start approach may be easier to follow for most women. However, a good practice is to recommend use of an additional form of contraception during the first cycle to maximize efficacy. Withdrawal bleeding can be expected within 3-5 days after completion of the 20- or 21-day regimen.

The serum levels of FSH and LH throughout the normal menstrual cycle are shown in Figure 33-2A. During a typical cycle under the combined oral contraceptive regimen (Fig 33-2B), there is no rise during the first half of the cycle; thus, follicle growth is either not initiated or, if initiated, recruitment does not occur, ovulation does not occur, and consequently there is no FSH and LH surge. During the sequential oral contraceptive regimen (Fig 33-2C), the estrogen stimulates LH secretion in an irregular manner. There is no concomitant early rise in FSH when progestin is added, and another LH surge usually is produced. When a progestin-only regimen (Fig 33-2D) is followed (eg, with the minipill; see Minipill section), there are multiple LH surges but no significant changes in FSH levels. For the reasons given, these oral contraceptive regimens significantly alter the physiologic hormonal balance. The minipill regimen causes the least derangement, but its efficacy as a contraceptive is less than that of combined oral contraception. Moreover, occasional amenorrhea may occur.

Advantages
Major noncontraceptive advantages derived from use of oral contraceptives in the U.S. alone include approximately 50,000 hospitalizations averted annually for conditions that include benign breast disease, retention cysts of the ovaries, iron deficiency anemia, and pelvic inflammatory disease. Studies in the U.S. and Great Britain showed that users of oral contraceptives have almost complete protection against ectopic pregnancies. Oral contraceptive use is estimated to prevent about 10,000 hospitalizations for this life-threatening complications annually in the U.S. alone.