616 Obstetrics and Gynecology Board Review •••
❍ What is Implanon?
Implanon is a progestin (etonogestrel)-containing implant placed in the upper arm. It protects against pregnancy
for 3 years.
❍ When should Implanon be inserted to minimize pregnancy risk?
Within 5 days of the onset of menstruation or 3 to 4 weeks after delivery.
❍ In progestin-only pill users, which women are at greatest risk of pregnancy?
Those who take their pill >3 hours late. The main mechanism of action is thickening of cervical mucus and thinning
the lining of the endometrium, which depends on taking the pill daily at the same time every day. Menstrual cycles
prior to pill use were ovulatory and whose cycles are least disturbed.
BARRIER METHODS
❍ Do all condoms protect against all sexually transmitted diseases (STDs)?
No. Condoms may permit the passage of viruses such as human papilloma virus (HPV) and herpes simplex virus
(HSV).
❍ What is the method failure rate of the condom?
Perfect use has a 2% failure rate versus actual use rates of about 18%.
❍ Are spermicidal condoms as effective as a condom plus intravaginal spermicide?
No. The dose delivered by a lubricated condom is much less than intravaginal spermicide.
❍ What is the rate of pregnancy after a condom breaks?
About 1 per 23 breaks. Rates of breakage are about 1 to 2 per 100 condoms used.
❍ What lubricants increase breakage?
Oil-based lubricants such as Vaseline, baby oil, and lotions. Heat can also break down condoms, so storing them in
a wallet or hot car is not recommended.
❍ What are the two components of spermicides?
Base or carrier (foam, cream, or jelly) and spermicidal chemical, usually nonoxynol-9.
❍ How do spermicides work?
They are surfactants that destroy the sperm cell membrane.
❍ How much time does it take for spermicidal suppositories to be effective?
10 to 15 minutes. The act of intercourse should ideally occur <20 minutes after insertion of the spermicide and no
30 minutes after.
❍ How quickly can sperm enter the cervical canal?
As soon as 15 seconds after ejaculation.