Contraception and Birth Control for USMLE Step 2

Simple handwritten Contraceptive (Birth Control) lecture for medical students taking the USMLE. Will be looking at how contraceptives work and the pharmacology. Also the different contraception methods, such as Oral contraceptive, Intrauterine Devices, Implants.

Contraception is a method of females to prevent pregnancies. There are several contraceptive methods, however, there is no 100% full proof method. Tier 1 failure rate is less than 1%, Tier 2 have a contraceptive failure rate 2-3% and finally tier 3 is the barrier method and they are about 80% effective.

Tier 1 is made up of Intrauterine devices (mirena, Copper), DMPA, Implanon (subcutaenous) and sterilization (tubal ligation or vesectomy). Tier 2 are the Oral Contraceptive Pills, Patches and Rings, and they are made up of comboniation or just progesterone. Tier 3 is the barrier methods include condoms, diaphragm and the spermicidies which prevents implantation. Can also prevent STDs and HPV.

Intrauterine devices are implantedin the uterus. They are made up of mirena and copper. Mirena secretes levonogestrel which is a type of progesterone that has three effects. Thickens the cervical mucosa which prevents sperm form ascending into the uterus. The endometrial wall is also thickened that decreases the chance of implantation. Increase tubal motility so it is not in blastocyst and it can’t implant into endometrium. Copper Intrauterine device leads to inflammation response which causes the same effects. Mirena can work up to five years, whereas copper can work for 10 years. In Mirena there will be decrease bleeding and cramping. However, Copper can increase bleeding and cramping. Contra-indications to Intrauterine Devices is pregnancy, history of breast cancer, leiomyomas, any uterine infection such as PID and endometritis, especially chlamydia. Any bleeding where the cause is unknown. Relative complications are anatomical uterine anomalies (size and shape), Heart Disease because sometimes perforates and then bleeding can affect the heart. Any history of ectopic pregnancy. Finally there may be complications such as expulsion of the device within 1 month. Perforation, ectopic pregnancy, infection (PID) which usually happens within first 2 months.

Sterilization and generally irreversible. Tubal ligation and vesectomy are the two methods. Vesectomies are more effective.

TIER 2 are the hormonal methods there are two types which are known as combined and progesterone only. In combined there is pill patch and ring. In Progesterone only there is pill injection and implant. No LH surge means there is no ovulation and there is atrophy of the endometrium and therefore there is no implantation possible. Cervix becomes thick and edematous and prevents sperm from coming in.

Combined method is when there is estrogen and progesterone. The pill can begin any day however effects won’t begin for 7 days. 21 days and 7 days off. Off days are for the withdrawal bleed. Also helps regulate and normalize the menstrual cycle. The nuvaring enters the vagina and slowly releases estrogen and progesterone. Every three weeks it needs to be removed for 1 week. Patch also slowly release estrogen and progesterone under the skin which gives 60% greater than pills.

Progestin only method in pill form is a daily pill that is continuous which causes irregular breakthrough bleeding. Injection form Depo-Medroxyprogesterone Acetate (DMPA) is injected into the skin and slowly released and it lasts for three months. Implanon is implanted subcutaneously and slowly releases etanogestrol and lasts for 3 years.