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INTRODUCTION

  • Contraception is the prevention of pregnancy by inhibiting sperm from reaching a mature ovum or by preventing a fertilized ovum from implanting in the endometrium.

MENSTRUAL CYCLE PATHOPHYSIOLOGY

  • The median menstrual cycle length is 28 days (range 21–40 days). Day 1 is the first day of menses and marks the beginning of the follicular phase. Ovulation usually occurs on day 14, followed by the luteal phase that lasts until the beginning of the next cycle.

  • The hypothalamus secretes gonadotropin-releasing hormone, which stimulates the anterior pituitary to secrete the gonadotropins follicle-stimulating hormone (FSH) and luteinizinig hormone (LH).

  • In the follicular phase, FSH levels increase and cause recruitment of a small group of follicles for continued growth. Between days 5 and 7, one of these becomes the dominant follicle, which later ruptures to release the oocyte. The dominant follicle develops increasing amounts of estradiol and inhibin, providing a negative feedback on the secretion of gonadotropin-releasing hormone and FSH.

  • The dominant follicle continues to grow and synthesizes estradiol, progesterone, and androgen. Estradiol stops the menstrual flow from the previous cycle, thickens the endometrial lining, and produces thin, watery cervical mucus. FSH regulates aromatase enzymes that induce conversion of androgens to estrogens in the follicle.

  • The pituitary releases a midcycle LH surge that stimulates the final stages of follicular maturation and ovulation. Ovulation occurs 24–36 hours after the estradiol peak and 10–16 hours after the LH peak.

  • The LH surge is the most clinically useful predictor of approaching ovulation. Conception is most successful when intercourse takes place from 2 days before ovulation to the day of ovulation.

  • After ovulation, the remaining luteinized follicles become the corpus luteum, which synthesizes androgen, estrogen, and progesterone (Fig. 30-1).

  • If pregnancy occurs, human chorionic gonadotropin prevents regression of the corpus luteum and stimulates continued production of estrogen and progesterone. If pregnancy does not occur, the corpus luteum degenerates, progesterone declines, and menstruation occurs.

FIGURE 30-1

Menstrual cycle events, idealized 28-day cycle. (Hatcher RA, Trussell J, Nelson AL, et al. Contraceptive Technology. 21st ed. Ardent, NY: Median, Inc.; 2015.)

(FSH, follicle-stimulating hormone; HCG, human chorionic gonadotropin; LH, luteinizing hormone.)

LH: 15 mIU/mL = 15 IU/L; 50−100 mIU/mL = 50−100 IU/L.

FSH: 10−12 mIU/mL = 10−12 IU/L; 25 mIU/mL = 25 IU/L. Estrogen: 40 pg/mL = ~150 pmol/L; 250−400

pg/mL = ~920−1470 pmol/L; 125−250 pg/mL = ~460−920 pmol/L.

Progesterone: 1 ng/mL = 3 nmol/L; 10−15 ng/mL = ~30−50 nmol/L.

Temperatures: 99°F = 37.2°C; 98°F = 36.7°C; 97°F = 36.1°C.

TREATMENT

  • Goal of Treatment: The prevention of pregnancy following sexual intercourse. Additional benefits from contraceptive use can also be realized (ie, sexually transmitted infections [STIs] prevention and menstrual cycle regulation).

Nonpharmacologic Therapy

  • A comparison of methods of nonhormonal contraception is shown ...

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