Parity and use-effectiveness with the contraceptive sponge

Understanding contraceptive failure

Contraceptive failure is a major source of unintended pregnancy. This chapter will review sources of data and measurement of contraceptive failure, summarize results from the literature on the risks of contraceptive failure during typical and perfect use for available methods of contraception, provide a tool for communicating risks of contraceptive failure to clients, examine determinants of contraceptive failure, and identify methodological pitfalls in the published literature.

Contraception for teenagers and young adults with cancer

Adolescence can be an extremely stressful time for all concerned. When this period is then compounded by the development of cancer, formidable and seemingly insurmountable problems may be perceived. Cancer in adolescence is relatively uncommon, with an annual incidence rate in western populations of approximately 150-200 per million. Five-year survival of patients diagnosed around 1990 exceeded 70% in the United Kingdom (UK) and United States of America (USA), and adolescents with cancer are likely to remain fertile. Further advances in therapeutic modalities are creating a generation of adolescents and young adults with cancer who can now aspire to the same sexual and reproductive activities as their healthy peers. This then raises the issue of avoidance of undesired pregnancy during and after treatment. This article aims to address the contraceptive needs of adolescents and young adults undergoing treatment for cancer.

Contraceptive failure in the United States

This review provides an update of previous estimates of first-year probabilities of contraceptive failure for all methods of contraception available in the United States. Estimates are provided of probabilities of failure during typical use (which includes both incorrect and inconsistent use) and during perfect use (correct and consistent use). The difference between these two probabilities reveals the consequences of imperfect use; it depends both on how unforgiving of imperfect use a method is and on how hard it is to use that method perfectly. These revisions reflect new research on contraceptive failure both during perfect use and during typical use.

Sponge versus diaphragm for contraception: a Cochrane review

The contraceptive vaginal sponge was developed as an alternative to the contraceptive diaphragm. Unlike the diaphragm, the sponge can be used for more than one coital act within 24 h without the insertion of additional spermicide, and it does not require fitting or a prescription from a physician. We conducted a systematic review of randomized controlled trials that compared the vaginal contraceptive sponge with the diaphragm used with a spermicide in order to evaluate the efficacy and continuation rates of the two devices. The sponge was statistically significantly less effective in preventing overall pregnancy than was the diaphragm in the two trials that met our inclusion criteria. The 12-month cumulative life table termination rates per 100 women for overall pregnancy were 17.4 for the sponge versus 12.8 for the diaphragm in the larger US trial, and 24.5 for the sponge and 10.9 for the diaphragm in the UK trial. Similarly, discontinuation rates at 12 months were higher with the sponge than with the diaphragm [odds ratio 1.3; 95% confidence interval (CI) 1.1-1.6]. Allergic-type reactions were more common with the sponge in both trials, although the frequency of discontinuation for discomfort differed in the two trials. Other randomized controlled trials will be needed to resolve the role of spermicides in preventing sexually transmitted infections or in causing adverse effects.

Sponge versus diaphragm for contraception

BACKGROUND

The contraceptive vaginal sponge was developed as an alternative to the contraceptive diaphragm. The sponge, made of polyurethane impregnated with nonoxynol-9 (1g), releases 125 mg of the spermicide over 24 h of use. Unlike the diaphragm, the sponge can be used for more than one coital act within 24 h without the insertion of additional spermicide, and the sponge does not require fitting or a prescription from a physician. How the sponge compares with the diaphragm in terms of efficacy and continuation is not clear.

OBJECTIVES

To compare the efficacy and continuation rates of the sponge compared with the diaphragm (used with nonoxynol-9 as a spermicide). Our a priori hypothesis was that the sponge would have a higher failure rate and higher discontinuation rates than the diaphragm.

SEARCH STRATEGY

We searched the computerized databases MEDLINE, EMBASE, Popline, LILACS, and the Cochrane Controlled Trials Register. In addition, we searched the reference lists of all potentially relevant articles and book chapters. We also contacted investigators involved with both trials identified to seek other published or unpublished trials.

SELECTION CRITERIA

We included randomized controlled trials comparing the vaginal contraceptive sponge (Today; Collatex) with any diaphragm used with nonoxynol-9 to prevent pregnancy.

DATA COLLECTION AND ANALYSIS

We examined the studies identified through the literature searches for possible inclusion and evaluated their methodological quality using the Cochrane guidelines. We contacted an author involved with both published trials for supplementary information about randomization and allocation concealment. We entered data into RevMan 4.1 and calculated Peto odds ratios for overall pregnancy and 12-month discontinuation using numbers of women as the denominator. We also abstracted 12-month cumulative life-table ratios for these same outcomes, but were unable to aggregate these data.

MAIN RESULTS

The sponge was statistically significantly less effective in both trials in preventing overall pregnancy than was the diaphragm. The 12-month cumulative life-table termination rates per 100 women for overall pregnancy were 17.4 for the sponge versus 12.8 for the diaphragm in the larger U.S. trial and 24.5 for the sponge and 10.9 for the diaphragm in the U.K. trial. Similarly, discontinuation rates at 12 months were higher with the sponge than with the diaphragm (odds ratio 1.3; 95% CI 1.1-1.6). Allergic-type reactions were more common with the sponge in both trials, although the frequency of discontinuation for discomfort differed in the two trials.

REVIEWER'S CONCLUSIONS

The sponge was less effective than the diaphragm in preventing pregnancy. Discontinuation rates were higher at 12 months as well. Other randomized controlled trials will be needed to resolve the role of spermicides in preventing sexually transmitted infections or in causing adverse effects.

Retrospective vs. prospective coital frequency and menstrual cycle length in a contraceptive effectiveness trial

PURPOSE

To determine how well information at enrollment would predict coital frequency and menstrual segment length during a prospective contraceptive effectiveness trial.

METHODS

We compared retrospective reports of monthly coital frequency and menstrual segment (cycle) length with prospective information for women participating in a contraceptive trial of the Reality((R)) female condom.

RESULTS

Participants reported slightly higher mean monthly coital frequency and slightly longer menstrual segments prior to the study than during the study (12.6 acts vs. 12.0 acts per month and 30.8 days vs. 28.4 days). We examined the actual distribution of differences between the retrospective and prospective measures and found considerable variability. Among the 195 participants studied, parous women were less likely to predict accurately menstrual segment length (OR 0.4; 95% CI 0.3--0.9), while older women were more likely to predict accurately coital frequency (OR 1.9; 95% CI 0.9--3.3).

CONCLUSIONS

Coital frequency and menstrual segment length vary considerably over time. Hence, prospective data collection is essential to accurately characterize these variations and to properly interpret results from contraceptive trials and other studies concerned with fecundability and hazards of reproduction.

Barrier methods of contraception

Despite the problems associated with coitus-dependent methods of contraception, barrier methods have an important role. The fact that they work as contraceptives without systemic effects makes them particularly appropriate for women with medical conditions that prevent the use of hormonal contraception. In addition, condoms and perhaps all barrier methods provide protection from sexually transmitted infections, making them essential for sexually active women at risk for STDs. Their continued importance is evidenced by the ongoing research to develop and improve barrier methods of contraception.

Influence of cycle variability and coital frequency on the risk of pregnancy

Researchers have cautioned against generalizing results from contraceptive trials because these studies rely on self-selected participants meeting strict selection criteria who may differ from typical users. Using information collected on daily diaries, we reanalyzed data from the recently completed Reality female condom clinical trial to evaluate factors that influence the probability of pregnancy. Noncompliant women, women with less variable menstrual cycles (17-43 days), and women engaging in intercourse frequently (> or = 11 acts per month) were more likely to conceive during this 6-month trial. The adjusted hazard ratios and 95% confidence intervals for these three covariates were 6.1 (2.0-18.7), 7.2 (1.0-54.3), and 2.0 (0.7-5.3), respectively. The strict selection criteria used in this study failed to recruit a homogeneous cohort with respect to factors that influence the risk of pregnancy. The overall pregnancy rate does not pertain to individual study participants, but rather represent average effects for a population with the particular mix of characteristics found in this study. In particular, we not only confirm the well known importance of compliance and the obvious role of frequency of intercourse, but also demonstrate that women with cycles outside the range of 17-43 days appear to be at a much lower risk of pregnancy.

Post-partum contraception

The choice of a post-partum contraceptive method depends on many factors, including the need for a temporary versus a permanent method, the infant feeding choice and the extent to which informed consent is made prior to delivery. For maximum protection, the non-breast-feeding woman should be protected from the fourth week post-partum, even if that means using a temporary method, such as condoms or spermicides, until her method of choice is procured. Combined oestrogen/progestin methods should be avoided by all women for 2-3 weeks to avoid elevating the risk of thromboembolism. Preparations containing oestrogen should be avoided altogether during lactation because they have been associated with a reduction in milk production. POPs, implants and injectables are appropriate regardless of infant feeding choice. They can be administered immediately post-partum in bottle-feeding women, but should ideally be postponed for 6 weeks in breast-feeding women. It is best to insert IUDs within 10 minutes of delivery of the placenta, in order to minimize the risk of IUD expulsion. Insertion immediately after expulsion of the placenta requires special training, and expulsion rates are reduced with the insertion experience of the practitioner. Breast-feeding is not associated with an increase in IUD expulsion or uterine perforation, and it is associated with fewer removals for bleeding or pain. Tubal sterilization is safe, convenient and cost-effective when performed immediately after delivery, but it requires extensive counselling and fully informed consent prior to the onset of labour to avoid potential regret over post-partum tubal ligation. If the procedure is performed immediately, any effect on the establishment of lactation may be minimized. LAM is a method that can only be used by breast-feeding women. It may prove to be a useful way to time the commencement of a second, less temporary contraceptive method. Natural family planning methods require a period of abstinence for the establishment and identification of the new symptoms of fertility. When LAM is used during this interval, the need for abstinence may be reduced significantly for breast-feeding women. Breast-feeding provides health benefits for the woman and her infant, as well as the best possible nutrition for the baby. The International Planned Parenthood Federation (1990) (among others) recommends that, 'As far as is practicable, all women should be advised and encouraged to breastfeed fully'. The infant feeding decision affects the choice of a contraceptive method, and this is an important reason for the woman's physician to be interested in her infant feeding choice.

Methodological pitfalls in the analysis of contraceptive failure

Although the literature on contraceptive failure is vast and is expanding rapidly, our understanding of the relative efficacy of methods is quite limited because of defects in the research design and in the analytical tools used by investigators. Errors in the literature range from simple arithmetical mistakes to outright fraud. In many studies the proportion of the original sample lost to follow-up is so large that the published results have little meaning. Investigators do not routinely use life table techniques to control for duration of exposure; many employ the Pearl index, which suffers from the same problem as does the crude death rate as a measure of mortality. Investigators routinely calculate 'method' failure rates by eliminating 'user' failures from the numerator (pregnancies) but fail to eliminate 'imperfect' use from the denominator (exposure); as a consequence, these 'method' rates are biased downward. This paper explores these and other common biases that snare investigators and establishes methodological guidelines for future research.

Parity and the effectiveness of the Today contraceptive sponge

A comparative study of the Today sponge and diaphragm conducted in the United States found a significantly higher pregnancy rate for parous compared with nulliparous sponge users. The results of other studies of the sponge failed to confirm this finding. Studies of other vaginal contraceptive methods conducted in the United States also have reported a higher pregnancy rate for parous users. None of these studies have evaluated adequately motivational and other factors that affect contraceptive choice and use. We conclude that the higher pregnancy rate among parous sponge users is unrelated to the sponge per se, and most likely reflects motivational factors related to future childbearing intentions.

Clinical acceptability, use-patterns and use-effectiveness of the vaginal contraceptive sponge and Neo Sampoon tablets--an international multi-center randomized clinical trial

This paper describes the results from a randomized clinical trial comparing the Collatex vaginal contraceptive sponge (a predecessor of the Today sponge) and Neo Sampoon foaming vaginal contraceptive tablets; the trial was conducted from 1979 to 1983 in four centers located in three countries (two in Yugoslavia and one each in Taiwan and Bangladesh). The sponge was associated with more insertion and retention problems than the tablet, especially in the two Asian centers. More Neo Sampoon users complained of a burning or stinging sensation. This complaint, however, seemed to be well-tolerated and was not a frequent reason for irregular use and/or discontinuation of use of the tablets. Clinically significant medical complications were rarely reported for either method. Sponge users were more likely to report irregular use than tablet users, primarily due to inconvenience of use. Rates of discontinuation at six months of use were also consistently higher among sponge users than Neo Sampoon users in the four centers. Life-table pregnancy rates at 12 months of use ranged from 3.8 to 18.2 per 100 sponge users and 6.2 to 29.9 per 100 Neo Sampoon users, based on data from the two Yugoslavian centers and the Taiwan center (data from the Bangladesh center were excluded from analysis of pregnancy rates). Practical implications of these findings are discussed.