Contraception Flashcards
contraception for the masses: how to make a pregnancy
*make an egg
*ovulate an egg
*make a sperm
*ejaculate a sperm
*get the 2 together
contraception for the masses: how to PREVENT a pregnancy
*don’t make an egg
*don’t ovulate the egg
*don’t make a sperm
*don’t ejaculate a sperm
*block them from getting together
egg vs. follicle
*medical word for egg = oocyte, which is the single cell female gamete
*an oocyte never exists alone; it is surrounded by and intimately linked to layers of granulosa cells and layers of theca cells
*the oocyte together with its surrounding granulosa and theca cells = follicle
how many follicles does a human ovary have?
*7 million follicles at 20 weeks gestation; 2 million at birth (most are primordial follicles); 400,000 at puberty; only 400 ovulated over the course of reproductive life with atresia of the others that accelerates after approx. age 35-40 until all are depleted at menopause
hypothalamic-pituitary-ovary axis
hypothalamus produces GnRH → GnRH stimulates anterior pituitary to produce and release FSH & LH → FSH & LH stimulate the ovary:
1. FSH stimulates GRANULOSA cells to produce ESTRADIOL
2. LH stimulates THECA cells after ovulation to produce PROGESTERONE
estradiol & progesterone act on the uterus (endometrium) to stimulate menstruation/bleeding
normal ovulatory cycle - feedback loops
- estradiol (from the granulosa cell) and all estrogens → negative feedback on FSH levels
- progesterone (from the theca cell) and all progestins → negative feedback on LH levels
underlying mechanism of oral combination estrogen-progesterone contraception: negative feedback loops
*giving estrogen → neg. feedback on FSH → do not recruit/make/mature the follicle
*giving progesterone → neg. feedback on LH (preventing LH surge) → do not OVULATE oocyte from the follicle
estrogens - definition
*a class of compounds that bind to the estrogen receptor; agonists
*main estrogens found naturally in humans: estradiol, estrone, estriol
*ethinyl estradiol = the estrogen found in OCPs
progestins - definition
*a class of synthetic compounds that bind to the progesterone receptor
*notably, these compounds have various affinity for estrogen, androgen, and mineralocorticoid receptors
*for contraception, your main desire is to use a progestin that is agonistic at the progesterone receptor in the hypothalamus & pituitary so that there is negative feedback on LH and no ovulation
estrogen & progesterone in contraception - actions
- estradiol/estrogen → negative feedback on FSH → FSH levels drop → follicles are not recruited and do not develop
- progesterone/progestin → negative feedback on LH → LH levels drop (no LH surge) → no ovulation
estrogens - effects on the endometrium
*proliferative effect on the endometrium
*great for sperm, work quickly, lose stability very quickly
progestins - effects on the endometrium
*stabilizing effect on the endometrium
*induces atrophy
*long term: bad for sperm / prevents sperm from getting through
note - if estrogen & progesterone are given together, PROGESTINS have the dominant effect long-term
estrogens - effects on cervical mucus
*estrogen makes cervical mucus thin, watery, stretchy, and a lovely place for sperm to thrive
progestins - effects on cervical mucus
*progestins make cervical mucus thick, sticky, and a hostile place for sperm (sperm get stuck and die)
note - if estrogen & progesterone are given together, PROGESTINS have the dominant effect long-term
mechanisms of progestins in contraceptives (systemic) - overall
- negative feedback on LH → prevents ovulation
- atrophic effect on endometrium, which is hostile to sperm, so the sperm die or become immobile (prevents oocyte & sperm from meeting)
- thick cervical mucus, which is hostile to sperm, so the sperm die or become immobile (prevents oocyte & sperm from meeting)
mechanisms of progestins in contraceptives (IUD) - overall
*the negative feedback on LH does NOT occur because the progestin is not absorbed systemically
*therefore, people with IUD’s still ovulate
*prevention of pregnancy is by the other 2 mechanisms: atrophy or endometrium + thickened cervical mucus
do contraceptives affect how many follicles an ovary has?
*NO - you are born with all the follicles you will ever have
*what a contraceptive CAN do is simply change how many you go on to mature or ovulate
*contraceptives also do not alter the rate of follicular atresia
contraceptive failure rates
*perfect use effectiveness: rate of effectiveness when the contraceptive method is always used consistently & correctly
*typical use effectiveness: rate of effectiveness in all couples using a method, both consistently and inconsistently
*Pearl Index = number of pregnancies that would occur per 100 women in 1 year
methods of contraception: withdrawal
*method of preventing pregnancy; prevent the egg & sperm from getting together
*perfect use 4% failure; typical use 22% failure rate
methods of contraception: rhythm method, natural family planning, fertility awareness
*method of preventing pregnancy; prevent the egg and sperm from getting together
*basal body temperature, cervical mucus method, sympothermal method
*requires a great amount of motivation and training
*requires regular menses
methods of contraception: Phexxi
*nonhormonal vaginal gel
*mechanism: maintains vaginal acidic pH, which immobilizes sperm
*NOT a spermicide
*must apply before intercourse, lasts for 1 hour
*expensive
methods of contraception: spermicides
*foams, creams, suppositories
*active ingredient: Nonoxyl 9, a surfactant that immobilizes sperm on contact by destroying cell membrane
*also a mechanical barrier
*need to be placed in vagina before each act of coitus
*may increase risk of viral transmission (HIV)
methods of contraception: contraceptive sponge
*traps & absorbs sperm
*sperm death: continuously releases spermicide to kill sperm
*physical barrier: covers the cervix so that sperm can’t reach the egg
*issues: UTIs, irritation, efficacy, cost
methods of contraception: cervical cap & diaphragm
*mechanism: physical barrier to sperm and spermicidal (spermicide use required)
*both diaphragm and cap require fitting an a prescription
*timing issues (insert before, leave in for minimum time post-intercourse)
*issues: UTIs, irritation, need for repeat spermicide, damaging effect of oil based lubricants
