Obstetrics and Gynecology Board Review Pearls of Wisdom

608 Obstetrics and Gynecology Board Review •••

Method

Percentage of Women

with Pregnancy Percent of

Women Continuing

Typical use at 1 Year

Lowest

Expected

Combined and progestin only pill 8 0.3 68

Ortho Evra patch 8 0.3 68

NuvaRing 8 0.3 68

DepoProvera 3 0.3 56

Intrauterine device (IUD)

Copper T 0.8 0.6 78

Levonorgestrel 0.2 0.2 80

Sterilization

Female 0.5 0.5 100

Male 0.15 0.10 100

Implanon 0.05 0.05 84

❍ What are the methods to measure the contraceptive efficacy?
Pearl index and life table analysis.

❍ True/False. The failure rates increase with duration of use with most contraceptive methods.
False. Failure rates actually decline with duration of use. The Pearl index is calculated as the pregnancy rate in a
population divided by 100 years of user exposure and therefore fails to accurately compare methods at various
durations of exposure. This limitation is overcome by using the method of life table analysis that gives the failure
rate for each month of use.

❍ What are the recommendations following vasectomy?
Barone et al. 2003 reported that azoospermia is more likely after 12 weeks (60%) than after 28 ejaculations (28%).
A more reliable way to document azoospermia is semen analysis. Other forms of contraception are recommended
until two semen samples show no motile sperm.