Contraceptive failure rates: new estimates from the 1995 National Survey of Family Growth

CONTEXT

Unintended pregnancy remains a major public health concern in the United States. Information on pregnancy rates among contraceptive users is needed to guide medical professionals' recommendations and individuals' choices of contraceptive methods.

METHODS

Data were taken from the 1995 National Survey of Family Growth (NSFG) and the 1994-1995 Abortion Patient Survey (APS). Hazards models were used to estimate method-specific contraceptive failure rates during the first six months and during the first year of contraceptive use for all U.S. women. In addition, rates were corrected to take into account the underreporting of induced abortion in the NSFG. Corrected 12-month failure rates were also estimated for subgroups of women by age, union status, poverty level, race or ethnicity, and religion.

RESULTS

When contraceptive methods are ranked by effectiveness over the first 12 months of use (corrected for abortion underreporting), the implant and injectables have the lowest failure rates (2-3%), followed by the pill (8%), the diaphragm and the cervical cap (12%), the male condom (14%), periodic abstinence (21%), withdrawal (24%) and spermicides (26%). In general, failure rates are highest among cohabiting and other unmarried women, among those with an annual family income below 200% of the federal poverty level, among black and Hispanic women, among adolescents and among women in their 20s. For example, adolescent women who are not married but are cohabiting experience a failure rate of about 31% in the first year of contraceptive use, while the 12-month failure rate among married women aged 30 and older is only 7%. Black women have a contraceptive failure rate of about 19%, and this rate does not vary by family income; in contrast, overall 12-month rates are lower among Hispanic women (15%) and white women (10%), but vary by income, with poorer women having substantially greater failure rates than more affluent women.

CONCLUSIONS

Levels of contraceptive failure vary widely by method, as well as by personal and background characteristics. Income's strong influence on contraceptive failure suggests that access barriers and the general disadvantage associated with poverty seriously impede effective contraceptive practice in the United States.

Pill method failures in women seeking abortion: fourteen years experience

AIMS

To document predisposing factors in 769 women who had inadvertently conceived while taking oral contraceptive pills reliably.

METHODS

Over a 14-year period, 1981-1995, two questionnaires were administered, one for women using the combined oral contraceptive pill (COC) and one for women using the progestogen only pill (POP).

RESULTS

More than one predisposing factor was usually present, the most common being diarrhoea and/or vomiting in 39.0%. Antibiotics had been prescribed in 20.5%. COC failure was associated with a high incidence of menstrual disturbance (37.1%). A history of a previous pill failure was obtained in 27.8%. Smoking was a risk factor for women on the COC. Only 6.0% became pregnant during the first month of pill use. As expected, POP users experienced a higher number of pill failures in proportion to the market share, but excess weight and time of taking did not appear to be risk factors. Most COCs failed according to the numbers expected from the market share.

CONCLUSIONS

Many pill failures could be averted by better information about known or suspected risk factors, especially gastrointestinal upset and interacting medications. Pill failure is one more reason to discourage smoking in COC users.

A case of failure of tubal sterilization using Pomeroy's technique

With reference to a case of pregnancy of a patient formerly subjected to tubal sterilization using Pomeroy's technique, the authors define the possibility for tubal stumps to recanalise. Despite the low percentage of failure in tubal sterilization using Pomeroy's technique, the authors conclude that it is advisable to make the earliest possible diagnosis of both intrauterine and extrauterine pregnancy on the basis of suspected symptoms in order to, especially for tubal pregnancies, avoid any tubal sterilization.

Patient noncompliance after vasectomy

OBJECTIVE

To determine the postoperative instruction compliance rate in men undergoing bilateral vasectomy.

DESIGN

Retrospective chart review.

SETTING

Private practice urological office.

PATIENT(S)

The records of all patients undergoing vasectomy were reviewed to determine the rate of compliance with postvasectomy follow-up instructions. It is our policy to have the patient continue to use some form of birth control until he achieves two consecutive negative semen analyses 1 month apart. In addition, we recommend a yearly semen analysis after achieving sterility to screen for the rare patient who recanalizes. Postvasectomy follow-up instructions are given to the patient both verbally and in writing.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

The records of 1,892 consecutive patients undergoing vasectomy were reviewed, and the results of semen analyses were noted to determine the rate of compliance with postvasectomy follow-up instructions.

RESULT(S)

Six hundred forty-four men (34%) never returned after vasectomy and, therefore, no semen analyses were available for examination. Six hundred nineteen men (33%) returned for a single semen analysis. Six hundred twenty-nine men (33%) returned for a second negative semen analysis. Only 60 men (3%) completed postvasectomy follow-up instructions and returned for a yearly semen analysis.

CONCLUSION(S)

The rate of compliance with postvasectomy follow-up instructions for determining sterility is poor.

Oral contraceptive failure rates and oral antibiotics

BACKGROUND

Despite anecdotal evidence of a possibility of decreased effectiveness of oral contraceptives (OCs) with some antibiotics, it is not known whether antibiotic use in dermatologic practices engenders any increased risk of accidental pregnancy.

OBJECTIVE

Our purpose was to examine the effect of commonly prescribed oral antibiotics (tetracyclines, penicillins, cephalosporins) on the failure rate of OCs.

METHODS

The records from three dermatology practices were reviewed, and 356 patients with a history of combined oral antibiotic/OC use were surveyed retrospectively. Of these patients, 263 also provided "control" data (during the times they used OCs alone). An additional 162 patients provided control data only.

RESULTS

Five pregnancies occurred in 311 woman-years of combined antibiotic/OC exposure (1.6% per year failure rate) compared with 12 pregnancies in 1245 woman-years of exposure (0.96% per year) for the 425 control patients. This difference was not significant (p = 0.4), and the 95% confidence interval on the difference (-0.81, 2.1) ruled out a substantial difference (> 2.1% per year). There was also no significant difference between OC failure rates for the women who provided data under both conditions, nor between the two control groups. All our data groups had failure rates below the 3% or higher per year, which are typically found in the United States.

CONCLUSION

The difference in failure rates of OCs when taken concurrently with antibiotics commonly used in dermatology versus OC use alone suggests that these antibiotics do not increase the risk of pregnancy. Physicians and patients need to recognize that the expected OC failure rate, regardless of antibiotic use, is at least 1% per year and it is not yet possible to predict in whom OCs may fail.

Contraceptive outcomes among adolescents prescribed Norplant implants versus oral contraceptives after one year of use

OBJECTIVE

Our goal was to evaluate both the continuation and pregnancy rates and the side effects experienced during the first year of use by adolescents who selected Norplant implants as compared with those who chose oral contraceptives for contraception. Furthermore, side effects experienced at 6 versus 12 months among Norplant implant users were compared to determine whether they diminished with continued use of this method.

STUDY DESIGN

We conducted a case-control study of 56 adolescents < or = 18 years old who selected implants as compared with 56 age-matched controls who chose oral contraceptive pills during the same time period.

RESULTS

Only 34% of patients prescribed oral contraceptives as compared with 91% of Norplant implant patients were still using their chosen method 1 year later. As a result 25% of oral contraceptive users became pregnant within 12 months as compared with none who selected Norplant implants. Side effects were reported by > 80% of patients in both groups, with menstrual irregularities reported more often by Norplant implant users than by oral contraceptive users (73% vs 5%, p = 0.01). Furthermore, Norplant implant users gained more weight than oral contraceptive users (8.7 vs 4.2 pounds) and were twice as likely to have an abnormal Papanicolaou smear. Finally, little diminution in side effects was observed during the second 6 months of Norplant implant use.

CONCLUSIONS

These data confirm that Norplant implants provide better protection against unintended pregnancy in an adolescent population but may be associated with more side effects. Clinicians should be aware of these findings so they can adequately counsel young patients about these two methods of contraception.

Contraceptive practices of women requesting termination of pregnancy: a study from China

In order to develop a program for prevention of unwanted pregnancies, we conducted a survey of contraceptive practices and reasons for contraceptive failures of 1520 women seeking abortion at eight large hospitals in Zheng Zhou City, Henan Province, P.R. China, during the period from March 1996 to May 1996. The most frequent cause of the unplanned pregnancy was contraceptive failure (71.9%) 61.7% (938) of these current pregnancies were potentially predictable by virtue of nonuse of contraception (427) or by recognition of contraceptive failures (511). Among the contraceptive failures, the proportion of condom mishaps was the highest (29.7%), next was IUD failures (23.5%), then rhythm miscalculation (15.9%). Most of abortion seekers (77.1%) used some contraceptive methods previously. But only 19.7% of them used a contraceptive method at the first sexual intercourse. Among 1520 abortion seekers. 57.6% had used condoms previously; 50.9% of the condom users had at least one instance of condom mishap. The rhythm method had been used by 31.7% of abortion seekers previously; 59.1% of the rhythm users had at least one instance of rhythm failure. Of the 16.8% of abortion seekers who had used pills, 58.0% of them had pill failures Among condom and pill failures, most of them (46.4% condom users and 56.0%, pill users) belonged to the users failure category (poor compliance). Of those seeking abortion 56.4% had experienced at least one instance of previous abortion; 5.3% had experienced previous abortions at least two times. Emergency contraception had been utilized by only 10 subjects prior to this current pregnancy.

Spermicide effects questioned by FDA panel

Spermicides clearly work better than no contraceptive at all, but there's no way to say how effective they are or whether women should opt for a gel, foam, suppository, or film, a scientific panel concluded. The advisors to the US Food and Drug Administration (FDA) heard disturbing evidence that women who rely on spermicides as their sole contraceptive have anywhere from a 9% to a 57% chance of becoming pregnant within a year. Spermicides appear to work best when used just 30 minutes before intercourse, said Dr. James Trussell of Princeton University. Nobody knows for sure how well spermicides work, and which work best, because the only studies ever performed were flawed. The manufacturers never proved how well their products work because they hit the market in 1950, before the FDA required such proof. The US National Institutes of Health (NIH) plans to begin a study comparing one brand of each type of commercially available spermicide to see how effective they are. The results will not be available for at least 4 years, so the FDA is debating what to tell consumers in the meantime and if that study will be enough. The FDA may soon change spermicide labels at least to rank the products as less effective than other contraceptives, Dr. Lisa Rarick, FDA reproductive health chief, said. Spermicides also should bear a warning that they may cause vaginal irritation, a condition one study suggests might increase a woman's chances of catching HIV, the scientific panel told the FDA. The same panel agreed, however, that spermicides can help protect women against two other sexually transmitted diseases, gonorrhea and chlamydia.

Emergency hormonal contraception usage in genitourinary medicine clinic attenders

OBJECTIVE

To assess the indications for usage of emergency hormonal contraception amongst a population of London genitourinary medicine clinic attenders.

METHODS

In a prospective study, 150 consecutive women receiving emergency hormonal contraception (EHC) were enrolled. The attending doctor completed a questionnaire of patient details and prescribed EHC with prophylactic prochlorperazine. Follow-up was arranged three weeks later, at which time outcomes and side-effects of therapy were recorded. For those women who did not reattended as planned case notes were reviewed at three months.

RESULTS

Of 150 women surveyed, 100 (66%) reported contraceptive method failure, 48 (32%) had used no contraception at the time of last sexual intercourse and two requested EHC after sexual assault. Ninety three (62%) reported condom failure, 7 (5%) oral contraceptive pill failure. Seventy five (50%) had used EHC before (range 1-10 times). Seventy one (47%) women reattended within three months. Five (3.3%) of the 150 women were pregnant; none of these cases had experienced nausea or vomiting whilst taking EHC. Side-effects were reported by 22 (31%) of the 71 patients who reattended. Nine (6%) women had been followed-up in the family planning advisory clinic. Of the 71 women who reattended, 39 (55%) reported that their preferred future method of contraception would be condoms. Of the 150 women 19 (13%) underwent tests for sexually transmissible infections within one month of presentation.

CONCLUSIONS

EHC usage in this population was associated with a failure rate of at least 3.3% and an overall side effect rate of 31%. Despite requests for emergency contraception because of condom failure many elected to continue using condoms as their preferred method of contraception. The majority of women (53%) did not return for follow-up or family planning advice, and so we believe that future contraceptive plans must be addressed at the time EHC is prescribed.

The male polyurethane condom: a review of current knowledge

Condoms are one of the oldest form of contraceptive and the best recognized form of protection against sexually transmitted diseases. Their use, however, is limited by both behavioral factors and device-related factors, including complaints about decreased sensitivity and sexual enjoyment. To address these limitations, a male condom made of polyurethane was developed. Polyurethane is a strong impermeable material with good heat transfer characteristics that is less susceptible to deterioration during storage than latex. Because little information is available comparing polyurethane and latex condoms in terms of consumer preferences as well as breakage and slippage, we reviewed four pre-marketing studies of polyurethane condoms, one of which included comparison to latex. No significant differences in slippage and breakage rates between latex and polyurethane condoms were reported in the study that included a latex comparator, and other studies of polyurethane condoms alone resulted in rates in the same range as published for latex condoms. Subjectively, consumers expressed significantly greater preference for the polyurethane condom over latex in regard to appearance, lack of smell, likelihood of slippage, comfort, sensitivity, natural look, natural feel, and overall. While additional testing is needed, these preliminary results suggest that the male polyurethane condom reviewed performed at least as well as latex condoms and is preferred by consumers. If preference translates to greater use, the male polyurethane condom may address important barriers that have been linked with inadequate condom use in the past. These results, however, may not be generalizable to other brands of polyurethane condom currently under development.

The determinants of IUD discontinuation in China: a discrete-time competing risk model analysis

This research examines the social, demographic, and family-planning-program factors that influence the occurrence of IUD discontinuation among Chinese women, using a sample of 14,639 IUD use segments from the 1988 Chinese National Survey of Fertility and Contraceptive Prevalence. A discrete-time competing-risk event history method is employed to identify the determinants of IUD discontinuation by five kinds of reasons: contraceptive failure, expulsion, switching method, side-effects and other nonmethod-related reasons. The predictors of IUD discontinuation suggest that a number of mechanisms are in operation. Some of the determinants may reflect the effects of the family planning program; some may illustrate women's physiological and biological reactions to IUD's; some may be related to women's previous history of contraceptive use; and still others may indicate social characteristics of women that lead them to have their IUD's removed.