Letter to the Editor

Dear Editor

In the article published earlier this year in Contraception [1], we provided estimates of contraceptive failure, both unadjusted and adjusted for underreporting of abortion, from the 2002 National Survey of Family Growth (NSFG) and revised estimates from the 1995 NSFG for the five most commonly used methods in the United States: injectable contraceptives, oral contraceptives (“the pill”), male condoms, fertility-awareness-based methods (“rhythm,” “calendar,” “mucus,” and “temperature” methods, “periodic abstinence” or “natural family planning”) and withdrawal. There were not enough uses of other methods in the 2002 NSFG data to allow separate estimates of contraceptive failure. However, there were enough uses of the diaphragm and spermicides in the 1995 NSFG to sustain separate analyses, and we present these results below, along with complete results for the other five methods in the 1995 NSFG (Table 1).

Table 1.

Probability of failure within the first 3, 6 and 12 months of typical contraceptive use in the United States: weighted data, both unadjusted and adjusted for underreporting of abortion in the 1995 NSFG

Method	Probability of failure, unadjusted			Probability of failure, adjusted			Unweighted na
	3 months	6 months	12 months	3 months	6 months	12 months
Injectable	1.1	1.1	2.9	0.8	2.3	5.4	209
Pill	1.1	2.9	6.7	2.2	4.6	8.8	2127
Diaphragm	1.1	4.4	8.0	2.2	5.9	11.5	165
Male condom	2.4	5.3	8.6	5.4	10.2	17.8	2909
Fertility-awareness	4.6	14.4	19.6	5.5	16.2	22.6	249
Spermicides	4.9	9.2	16.4	8.5	16.8	28.2	272
Withdrawal	5.8	12.5	18.7	9.7	17.0	28.4	438
All methods	2.6	5.4	9.2	4.6	8.7	14.9	6839

^aNumber of contraceptive-use segments.