Contraception basics for the USMLE CK exam
Here are some contraception basics you will surely see on the CK exam. There are not too many tricks thrown around with this topic, a general understanding can provide you with 2-3 easy points in this area.
Oral contraceptives that combine progestin and estrogen
- Estrogen suppresses FSH, which prevents selection and maturation of a dominant follicle.
- Progestin works by suppressing LH, which inhibits ovulation. It also thickens cervical mucosa which further prevents the ability of semen to pass into the uterus.
- Together, they inhibit pregnancy by thinning the endometrial lining and resulting in light or misses menses.
Phasic vs. Monophasic Pills:
- Phasic pills vary the ratio of estrogen and progestin. This decreases the dose of hormone given but it increases the risk of breakthrough bleeding
- Monophasic pills deliver a constant dose of estrogen and progestin throughout the month
** Following cessation of OCP’s, fertilization usually resumes immediately. A small percentage of users will experience a period of infertility, known as “postpill amenorrhea”
Advantages and Disadvantages of OCP’s
Alternatives to OCP’s
- Progestin-only pills – “mini-pills”
- Depo-Provera – IM injection lasts for 14 weeks
- Norplant – subcutaneous implant lasts up to 5 years
- Intrauterine device à device left in place for several years
- Emergency Contraception à progestin/estrogen taken within 72hr
This covers the basics you should know and understand when it comes to very basic concepts regarding contraception.