FROM VITAL & HEALTH STATISTICS OF THE NATIONAL CENTER FOR HEALTH STATISTICS 

U.S. DEPARTMENT OF HEALTH, EDUCATION, AND WELFARE � Public Health Service I Number 26 = Awil 6,1978 

Contraceptive Efficacy Among Married Women 15-44 

Years of Age in the United States, 1970-731 

In the 3-year period 1970-73, 7.3 percent of Table 1. First year contraceptive failure rates per 100 married 

U.S. married women who sought to delay their vvomen aged 15-44 years, by whether contraception was intended to prevent or delay pregnancy, with corresponding 

next wanted child became unintentionally preg- standard errors United States, 1970-73 

nant I I 

lowing initiation of use (table 1). OnIy 3.7 per- intention of Failure rate Standard 

cent of those who had decided to terminate contraception per 100 women errorl 

childbearing failed to achieve that goal during 

the first year of contraception after deciding to Prevent .... . ... .. .. .. . ... 3.7 0.5 

prevent future births. Tilde these rates may Delay .. . .. ... .. ..... . .. ... 7.3 0.7 

while using contraception within 1 year fol­

� imply acute problems for the individuals who 1T’h~~e are provisional estimates of standard errors. See Tech-


did experience contraceptive failure, they are an nical Notes.


indicator of the high degree of effectiveness of


contraceptive use considered in the aggregate. tember 13, 1973. Respondents were selected by


The data presented here are extracted from a a multistage, area pro babiIit y, cross-sectional 

forthcoming report on contraceptive use effec- sample of households in the conterminous 

tiveness in the United States. They are based on United States. It should be emphasized that the 

Cycle I of the National Survey of Family statistics reported here do not pertain to a samGrowth (NSFG), conducted by the NationaI ple of all contraceptors but rather to a sample of 

Center for Health Statistics. The FEFG was de- wome’n Ivho were both married and contracepsigned to provide information about fertility, tive users for at least 1 month during the 3-year 

family planning intentions and activity, and period, tJuly 1, 1970, through .July 1, 1973. 

other aspects of maternaI and chikl health which The contraceptive failure rates for the varare closely reIated to childbearing. Data on each ious methods reported here are the probabilities 

of these topics were collected in personaI inter- of a contraceptive failure during the first year a 

views with approximately 9,800 women aged method was used. They were computed u-a 

15-44 years who had ever been married or who muItip Ie-increment, multiple-decrement Iif&, 

had children of their own living in the house- tabIe procedure. A contraceptive failure ochold. Interviews were conducted between July curred if the onset of pre~ancy was reported as 

1973 and February 1974; the midpoint was Sep- occurring prior to the termination of contraception. For the calculation of use effectiveness 

during the 3-year period prior to the survey, all 

1This report was prepared by Kathleen Ford, Ph.D., intervals of contraceptive use (including sterilizaDivision of Vital Statistics. The information in this re- tion) occurring during a continuous marriage 

port was extracted from the report “Contraceptive Effi­


cacy Among Married Women in the United States, were considered. It should be kept in mind that


1970 -1973,” by Barbara Vaughan, James Trussell, Jane these rates of use effectiveness of contraceptive 

@ Menken, and EIise F. Jones, which will be published in methods reflect patient misuse as weIl as method 

Series 23 of the Vital and Health Statistics series. failure. 
2 aduancedata . 

The partictdar method of contraception has 

long been observed to affect failure rates. Sterilization was by far the most successful method, 

with no failures recorded (table 2). The failure 

rate for the pill was 2.0, representing 2.0 failures 

per 100 women in the first year of use. Failure 

rates for the IUD (4.2), condom (10.1), and 

diaphragm (13. 1) follow in order of decreasing 

use effectiveness. 

These rates are standardized by the intention 

of use (those seeking to delay their next wanted 

birth and those seeking to prevent any further 

births). Since intention has been found to influence success with a method and different 

methods attract varying proportions of couples 

seeking to delay or prevent the next pregnancy, 

such standardization was necessary for proper 

comparison of me,thod failure rates. 

Table 2. First year contraceptive failure rates per 100 married 

women aged 15-44 years standardized by intention of contraception, by type of contraceptive used, with corresponding standard errors: United States, 1970-73 

I I 

Type of 

contraceptive Failure rate Standard 

used per 100 women errorl 

Sterilization . ... .. ... .. 0.0 

Pill .. .. .. .. ... ... .. .... .. .. . 2.0 0,4 

IUD ..... . .. ... .. . .. .. .. . .. 4.2 1.2 

Condom ...... ... .... . .. 10.1 1.7 

Foam, cream, or 

jelly ... .. .. ... ... . .... .. 14,9 2.1 

Diaphragm .... . ... .... . 13.1 3.8 

Rhythm .. . .. ... .. .. .... . 19.1 4.0 

All other 

methods .. . .... . . .... 10.8 2.9 

,

‘These are provisional estimates of standard errors. See Technical Notes. 

TECHNICAL NOTES 

DESIGN OF THE SURVEY: The National Survey of Family Growth (NSFG), initiated in 

1971, was designed to provide data on fertility, 

family planning, and related aspects of matermd 

and child health. Fieldwork for Cycle I was 

carried out by the National Opinion I?esearch 

Center in 1973 and early 1974, with September 

13, 1973, as the midpoint of the interviewing. 

A multistage probability sample of women 

in the noninstitutional population of the conterminous United States was used. Approximately 33,000 households were screened to 

identify the sample of women who would be 

eligible for the NSFG, i.e., women aged 15-44 

years who were either currently married, previously married, or never married but with natural children presently living in the household. 

In households with m-ore than one eligible woman, a random procedure was used to select only 

one to be interviewed. Since the interviews were 

always conducted with the sample person, the 

term “respondent “ is used throughout this report as synonymous with sample person. Interviews were completed for 3,856 black women 

and for 5,941 women of other races. A detailed 

description of the sample design is presented in 

“National Survey of Family Growth, Cycle I: 

Sample Design, Estimation Procedures, and Variance Estimation,” Series 2, No. 76 in the Vital 

and Health Statistics series. 

The interviews were highly focused on the 

respondents’ marital and pregnancy histories, on 

their use of contraception and the planning status of each pregnancy, on their intentions regarding the number and spacing of future births, 

on maternity and family planning services, and 

on a broad range of social and economic characteristics. While the interviews varied greatly in 

the time required for their completion, they 

averaged about 70 minutes. Quality control procedures were applied at all stages of the survey. 

These included a verification of listing completeness with unlisted dwelling units being brought 

into the sample, a preliminary field review of 

completed questionnaires for possible missing 

data or inaccurate administration, a 10-percent 

sample recheck of all households screened in the 

survey, observation of interviews in the field, 

and an independent recoding of a 5-percent subsample of completed interviews. 

RELIABILITY OF ESTIMATES: Since the statistics presented in this report are based on a 

sample, they may differ somewhat from the fig- e 

ures that would have been obtained if a com-
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ackmeMa3 — 

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plete census had been taken using the same questionnaires, instructions, interviewing personnel, 

and field procedures. This chance difference between sample results and a complete count is 

referred to as sampling error. In addition, the 

results are subject to nonsampling error due to 

respondent misreporting, data processing mistakes, and nonresponse. It is very difficult, if not 

impossible, to obtain accurate measures of nonsampling errors. These types of error were kept 

to a minimum by the quality control procedures 

and other methods incorporated into the survey 

design and administration. 

Sampling error, or the extent to which samples may differ by chance from a complete 

count, is measured by a statistic called the 

standard error of the estimate. The standard errors presented in this report are provisional estimates based on variances calculated for other 

life table estimates from this survey. 

The chances are about 68 out of 100 that an 

estimate from the sample would differ from a 

complete census by less than the standard error. 

The chances are about 95 out of 100 that the 

differences between the sampIe estimate and a 

complete count would be less than twice the 

standard error. 

DEFINITIONS OF TERMS 

Contraceptive use effectiveness.–In this report, use effectiveness is defined as the effectiveness of a method when it is being used. 

Contraceptive failure, the type of method termination which was the focus of this study, occurred if the date of stopping contraception 

came after the month, a pregnancy began, and 

the respondent said she had not stopped at the 

time she became pregnant. Periods of time when 

the respondent was not married as weIl as 

periods of time when the respondent was married but reported that she was not having intercourse were excluded from the calculations. 

Intention. –A method use interval was classified as a delay interval if the woman’s motive for 

using a contraceptive was to delay her next pregnancy. If her intentions were to have no more 

chiklren, the interval was classified as a Prevent 

interval. 

SYMBOLS 

Data not available 

Category not applicable . . . 

Quantity zero 

Quantity more than Obut less than 0.05— 0.0 

Figure does not meet .itandards of * reliability or pre~lon 
4 achtancedata 

Recent Issues of Advance Data From Vital and Health Statistics 

No. 25. Office Vkits to Doctors of Osteopathy: Na- No. 22. Office Vkits by Persons Aged 65 and Over: 

t i o nal Ambulatory Medical Care Survey, National Ambulatory Medical Care Survey, 

United States, 1975 (Issued: March 22, 1978) United States, 1975 (Issued: March 22, 1978) 

No. 24. Utilization of Selected Medical Practitioners: No. 21. Selected Fhdings of Dietary Food ConsumpUnited States, 1974 (Issued: March 24, 1978) tion Profiles of Persons 1-74 Years of Age in 

the United States, 1971-74 (In preparation) 

No. 23.	 Office Visits to General Surgeons: National 

Ambulatory Medical Care Survey, United 

States, 1975 (Issued: March 24, 1978) 

A complete list of Advance Data From Vital and Health Statkts”cs k available from the Scientific and Technical 

Information Branch. 

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