Blinding in randomised trials: hiding who got what

Blinding embodies a rich history spanning over two centuries. Most researchers worldwide understand blinding terminology, but confusion lurks beyond a general comprehension. Terms such as single blind, double blind, and triple blind mean different things to different people. Moreover, many medical researchers confuse blinding with allocation concealment. Such confusion indicates misunderstandings of both. The term blinding refers to keeping trial participants, investigators (usually health-care providers), or assessors (those collecting outcome data) unaware of the assigned intervention, so that they will not be influenced by that knowledge. Blinding usually reduces differential assessment of outcomes (information bias), but can also improve compliance and retention of trial participants while reducing biased supplemental care or treatment (sometimes called co-intervention). Many investigators and readers naïvely consider a randomised trial as high quality simply because it is double blind, as if double-blinding is the sine qua non of a randomised controlled trial. Although double blinding (blinding investigators, participants, and outcome assessors) indicates a strong design, trials that are not double blinded should not automatically be deemed inferior. Rather than solely relying on terminology like double blinding, researchers should explicitly state who was blinded, and how. We recommend placing greater credence in results when investigators at least blind outcome assessments, except with objective outcomes, such as death, which leave little room for bias. If investigators properly report their blinding efforts, readers can judge them. Unfortunately, many articles do not contain proper reporting. If an article claims blinding without any accompanying clarification, readers should remain sceptical about its effect on bias reduction.

Allocation concealment in randomised trials: defending against deciphering

Proper randomisation rests on adequate allocation concealment. An allocation concealment process keeps clinicians and participants unaware of upcoming assignments. Without it, even properly developed random allocation sequences can be subverted. Within this concealment process, the crucial unbiased nature of randomised controlled trials collides with their most vexing implementation problems. Proper allocation concealment frequently frustrates clinical inclinations, which annoys those who do the trials. Randomised controlled trials are anathema to clinicians. Many involved with trials will be tempted to decipher assignments, which subverts randomisation. For some implementing a trial, deciphering the allocation scheme might frequently become too great an intellectual challenge to resist. Whether their motives indicate innocent or pernicious intents, such tampering undermines the validity of a trial. Indeed, inadequate allocation concealment leads to exaggerated estimates of treatment effect, on average, but with scope for bias in either direction. Trial investigators will be crafty in any potential efforts to decipher the allocation sequence, so trial designers must be just as clever in their design efforts to prevent deciphering. Investigators must effectively immunise trials against selection and confounding biases with proper allocation concealment. Furthermore, investigators should report baseline comparisons on important prognostic variables. Hypothesis tests of baseline characteristics, however, are superfluous and could be harmful if they lead investigators to suppress reporting any baseline imbalances.

Generation of allocation sequences in randomised trials: chance, not choice

The randomised controlled trial sets the gold standard of clinical research. However, randomisation persists as perhaps the least-understood aspect of a trial. Moreover, anything short of proper randomisation courts selection and confounding biases. Researchers should spurn all systematic, non-random methods of allocation. Trial participants should be assigned to comparison groups based on a random process. Simple (unrestricted) randomisation, analogous to repeated fair coin-tossing, is the most basic of sequence generation approaches. Furthermore, no other approach, irrespective of its complexity and sophistication, surpasses simple randomisation for prevention of bias. Investigators should, therefore, use this method more often than they do, and readers should expect and accept disparities in group sizes. Several other complicated restricted randomisation procedures limit the likelihood of undesirable sample size imbalances in the intervention groups. The most frequently used restricted sequence generation procedure is blocked randomisation. If this method is used, investigators should randomly vary the block sizes and use larger block sizes, particularly in an unblinded trial. Other restricted procedures, such as urn randomisation, combine beneficial attributes of simple and restricted randomisation by preserving most of the unpredictability while achieving some balance. The effectiveness of stratified randomisation depends on use of a restricted randomisation approach to balance the allocation sequences for each stratum. Generation of a proper randomisation sequence takes little time and effort but affords big rewards in scientific accuracy and credibility. Investigators should devote appropriate resources to the generation of properly randomised trials and reporting their methods clearly.

Case-control studies: research in reverse

Epidemiologists benefit greatly from having case-control study designs in their research armamentarium. Case-control studies can yield important scientific findings with relatively little time, money, and effort compared with other study designs. This seemingly quick road to research results entices many newly trained epidemiologists. Indeed, investigators implement case-control studies more frequently than any other analytical epidemiological study. Unfortunately, case-control designs also tend to be more susceptible to biases than other comparative studies. Although easier to do, they are also easier to do wrong. Five main notions guide investigators who do, or readers who assess, case-control studies. First, investigators must explicitly define the criteria for diagnosis of a case and any eligibility criteria used for selection. Second, controls should come from the same population as the cases, and their selection should be independent of the exposures of interest. Third, investigators should blind the data gatherers to the case or control status of participants or, if impossible, at least blind them to the main hypothesis of the study. Fourth, data gatherers need to be thoroughly trained to elicit exposure in a similar manner from cases and controls; they should use memory aids to facilitate and balance recall between cases and controls. Finally, investigators should address confounding in case-control studies, either in the design stage or with analytical techniques. Devotion of meticulous attention to these points enhances the validity of the results and bolsters the reader's confidence in the findings.

Noncontraceptive health benefits of intrauterine devices: a systematic review

Most women and their clinicians are unaware that IUDs confer important noncontraceptive health benefits. This review summarizes the evidence from published articles on this topic. We conducted a series of systematic literature searches to identify articles on the noncontraceptive health benefits of IUD use. We reviewed the potentially pertinent ones for content, grouped them according to type of IUD, and evaluated them using the U.S. Preventive Services Task Force rating system. Over 500 titles were identified and several hundred abstracts were reviewed. Use of nonhormonal IUDs (plastic and copper) was associated with a decrease in endometrial cancer. The levonorgestrel intrauterine system can treat a variety of gynecological disorders, including menorrhagia and anemia. The levonorgestrel system has also been used successfully as part of hormone replacement therapy, as adjuvant therapy with tamoxifen, and as an alternative to hysterectomy for women with bleeding problems. Like oral contraceptives, intrauterine contraceptives confer important noncontraceptive health benefits.

Cohort studies: marching towards outcomes

A cohort study tracks two or more groups forward from exposure to outcome. This type of study can be done by going ahead in time from the present (prospective cohort study) or, alternatively, by going back in time to comprise the cohorts and following them up to the present (retrospective cohort study). A cohort study is the best way to identify incidence and natural history of a disease, and can be used to examine multiple outcomes after a single exposure. However, this type of study is less useful for examination of rare events or those that take a long time to develop. A cohort study should provide specific definitions of exposures and outcomes: determination of both should be as objective as possible. The control group (unexposed) should be similar in all important respects to the exposed, with the exception of not having the exposure. Observational studies, however, rarely achieve such a degree of similarity, so investigators need to measure and control for confounding factors. Reduction of loss to follow-up over time is a challenge, since differential losses to follow-up introduce bias. Variations on the cohort theme include the before-after study and nested case-control study (within a cohort study). Strengths of a cohort study include the ability to calculate incidence rates, relative risks, and 95% CIs. This format is the preferred way of presenting study results, rather that with p values.

Bias and causal associations in observational research

Readers of medical literature need to consider two types of validity, internal and external. Internal validity means that the study measured what it set out to; external validity is the ability to generalise from the study to the reader's patients. With respect to internal validity, selection bias, information bias, and confounding are present to some degree in all observational research. Selection bias stems from an absence of comparability between groups being studied. Information bias results from incorrect determination of exposure, outcome, or both. The effect of information bias depends on its type. If information is gathered differently for one group than for another, bias results. By contrast, non-differential misclassification tends to obscure real differences. Confounding is a mixing or blurring of effects: a researcher attempts to relate an exposure to an outcome but actually measures the effect of a third factor (the confounding variable). Confounding can be controlled in several ways: restriction, matching, stratification, and more sophisticated multivariate techniques. If a reader cannot explain away study results on the basis of selection, information, or confounding bias, then chance might be another explanation. Chance should be examined last, however, since these biases can account for highly significant, though bogus results. Differentiation between spurious, indirect, and causal associations can be difficult. Criteria such as temporal sequence, strength and consistency of an association, and evidence of a dose-response effect lend support to a causal link.

Descriptive studies: what they can and cannot do

Descriptive studies often represent the first scientific toe in the water in new areas of inquiry. A fundamental element of descriptive reporting is a clear, specific, and measurable definition of the disease or condition in question. Like newspapers, good descriptive reporting answers the five basic W questions: who, what, why, when, where. and a sixth: so what? Case reports, case-series reports, cross-sectional studies, and surveillance studies deal with individuals, whereas ecological correlational studies examine populations. The case report is the least-publishable unit in medical literature. Case-series reports aggregate individual cases in one publication. Clustering of unusual cases in a short period often heralds a new epidemic, as happened with AIDS. Cross-sectional (prevalence) studies describe the health of populations. Surveillance can be thought of as watchfulness over a community; feedback to those who need to know is an integral component of surveillance. Ecological correlational studies look for associations between exposures and outcomes in populations-eg, per capita cigarette sales and rates of coronary artery disease-rather than in individuals. Three important uses of descriptive studies include trend analysis, health-care planning, and hypothesis generation. A frequent error in reports of descriptive studies is overstepping the data: studies without a comparison group allow no inferences to be drawn about associations, causal or otherwise. Hypotheses about causation from descriptive studies are often tested in rigorous analytical studies.

An overview of clinical research: the lay of the land

Many clinicians report that they cannot read the medical literature critically. To address this difficulty, we provide a primer of clinical research for clinicians and researchers alike. Clinical research falls into two general categories: experimental and observational, based on whether the investigator assigns the exposures or not. Experimental trials can also be subdivided into two: randomised and non-randomised. Observational studies can be either analytical or descriptive. Analytical studies feature a comparison (control) group, whereas descriptive studies do not. Within analytical studies, cohort studies track people forward in time from exposure to outcome. By contrast, case-control studies work in reverse, tracing back from outcome to exposure. Cross-sectional studies are like a snapshot, which measures both exposure and outcome at one time point. Descriptive studies, such as case-series reports, do not have a comparison group. Thus, in this type of study, investigators cannot examine associations, a fact often forgotten or ignored. Measures of association, such as relative risk or odds ratio, are the preferred way of expressing results of dichotomous outcomes-eg, sick versus healthy. Confidence intervals around these measures indicate the precision of these results. Measures of association with confidence intervals reveal the strength, direction, and a plausible range of an effect as well as the likelihood of chance occurrence. By contrast, p values address only chance. Testing null hypotheses at a p value of 0.05 has no basis in medicine and should be discouraged.

Terbutaline pump maintenance therapy after threatened preterm labor for preventing preterm birth

BACKGROUND

Women with preterm labor that is arrested with tocolytic therapy are at increased risk of recurrent preterm labor. Terbutaline pump maintenance therapy has been given to such women to decrease the risk of recurrent preterm labor, preterm birth, and its consequences.

OBJECTIVES

To determine the effectiveness and safety of terbutaline pump maintenance therapy after threatened preterm labor in preventing preterm birth and its complications.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (searched May 2002) and the Cochrane Controlled Trials Register (Cochrane Library Issue 2, 2002).

SELECTION CRITERIA

Randomized trials comparing terbutaline pump maintenance therapy with alternative therapy, placebo, or no therapy after threatened preterm labor.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the studies for inclusion and then extracted data from eligible studies.

MAIN RESULTS

We included two studies. Terbutaline pump maintenance therapy did not appear to offer any advantages over the saline placebo pump or oral terbutaline maintenance therapy in preventing preterm births by prolonging pregnancy or its complications among women with arrested preterm labor. The weighted mean difference (WMD) for gestational age at birth was -0.1 weeks (95% confidence interval (CI) -1.7 to 1.4) for terbutaline pump therapy compared with saline placebo pump for both trials combined and 1.4 weeks (95% CI -1.1 to 3.9) for terbutaline pump versus oral terbutaline therapy for the first trial. The second trial reported a relative risk (RR) of 1.17 (95% CI 0.79 to 1.73) of preterm birth (less than 37 completed weeks) and a RR of 0.97 (95% CI 0.51 to 1.84) of very preterm birth (less than 34 completed weeks) for terbutaline pump compared with saline placebo pump. Terbutaline pump therapy also did not result in a higher rate of therapy continuation or a lower rate of infant complications. No data were reported on long-term infant outcomes, costs, or maternal assessment of therapy.

REVIEWER'S CONCLUSIONS

Terbutaline pump maintenance therapy has not been shown to decrease the risk of preterm birth by prolonging pregnancy. Furthermore, the lack of information on the safety of the therapy, as well as its substantial expense, argues against its role in the management of arrested preterm labor. Future use should only be in the context of well-conducted, adequately powered randomized controlled trials.

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.

Cervical cap versus diaphragm for contraception

BACKGROUND

The cervical cap and the diaphragm are vaginal barrier contraceptive methods that prevent pregnancy by covering the cervix. The two devices also act as a reservoir for spermicide. The cervical cap is smaller and can remain in place longer than the diaphragm. Two types of cervical caps, the Prentif cap and the FemCap, have been compared to the diaphragm in randomized controlled trials.

OBJECTIVES

The review seeks to evaluate the contraceptive efficacy, safety, discontinuation, and acceptability of the cervical cap with that of the diaphragm.

SEARCH STRATEGY

We searched MEDLINE, Popline, Cochrane Controlled Trials Register, EMBASE, and LILACS for randomized controlled trials of cervical caps, and we reviewed the references of the included publications. Also, we wrote to the manufacturers and known investigators to request information about any other published or unpublished trials not found in our search.

SELECTION CRITERIA

All randomized controlled trials in any language comparing a cervical cap with a diaphragm were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

All titles and abstracts located in the literature searches were assessed, and articles identified for inclusion were independently abstracted by two reviewers. Data were entered and analyzed with RevMan 4.1, and a second reviewer verified the data entered. Outcome measures include contraceptive efficacy, safety, discontinuation, and acceptability. Outcomes were calculated as Peto odds ratios with 95 percent confidence intervals using women as the denominators. Life-table and Kaplan-Meier cumulative rate ratios for selected measures were also presented in "Additional Tables."

MAIN RESULTS

The Prentif cap was comparable to the diaphragm in preventing pregnancy, but the FemCap was not as effective in preventing pregnancy as its comparison diaphragm. The curves for the life-table cumulative pregnancy rates through 24 months for the Prentif cap and the diaphragm were not statistically significantly different (p-value of 0.39). However, the six-month Kaplan-Meier cumulative pregnancy rates for the FemCap and the diaphragm did not meet the a priori definition of clinical equivalence. The Prentif cap had a higher proportion of Class I to Class III cervical cytologic conversions at the three-month visit than the diaphragm; the odds ratio was 2.3 (95% CI, 1.0-5.1). The FemCap trial did not find differences in Papanicolaou smear results between the cap and diaphragm groups. Prentif cap users had a lower odds ratio of vaginal ulcerations or lacerations (0.3; 95% CI, 0.1-0.7) than diaphragm users. FemCap users had a higher odds ratio of blood in the device on removal (2.3; 95% CI, 1.3-4.1), but a lower odds ratio of urinary tract infections (0.6; 95% CI, 0.4-1.0) than those in the diaphragm group. In the FemCap trial, similar proportions of women reported liking their assigned device "somewhat" or "a lot" at the two-week interview. However, FemCap users were less likely than the diaphragm users to state that they were "probably" or "definitely" likely to use the device alone after completing the trial (odds ratio of 0.5; 95% CI, 0.3-0.7) or that they would recommend it to a friend (odds ratio of 0.5; 95% CI, 0.3-0.8).

REVIEWER'S CONCLUSIONS

The Prentif cap was as effective as its comparison diaphragm in preventing pregnancy, but the FemCap was not. Both cervical caps appear to be medically safe.

Insertion of an intrauterine contraceptive device after induced or spontaneous abortion: a review of the evidence

OBJECTIVE

Assess the safety and efficacy of intrauterine contraceptive device (IUCD) insertion immediately after induced or spontaneous abortion.

DESIGN

Systematic search for randomised trials that had at least one treatment arm that involved IUCD insertion immediately after an induced or spontaneous miscarriage using Medline, Popline, EMBASE, and review articles supplemented by correspondence with investigators.

POPULATION

Women of any age or gravidity who had an IUCD inserted immediately after evacuation for spontaneous or induced abortion.

METHODS

Articles were abstracted and the raw data from tables were analysed with RevMan 3.1 software. We focused on Tietze-Potter gross life table probabilities with denominators of person-time of exposure.

MAIN OUTCOME MEASURES

Rates of perforation, expulsion, pelvic inflammatory disease, contraceptive failure, and method continuation.

RESULTS

Complication rates for immediate post-abortal IUCD insertion were low. Perforation was rare with a rate of approximately one per 1,000 insertions. One year gross cumulative expulsion rates ranged from 1.8% to 12.6%, pregnancy rates from 0.6% to 2.1%, and continuation rates from 54% to 90%. The net discontinuation rate due to pelvic inflammatory disease was low, ranging from 0.0 to 0.8 per 100 women at one year. Increasing gestational age at insertion was associated with increased expulsion rates.

CONCLUSIONS

Post-abortal IUCD insertion is safe and effective. The risks of perforation, expulsion, pelvic inflammatory disease and contraceptive failure were low and similar to those reported for interval insertion. Second trimester gestational age is associated with an increased risk of expulsion. Immediate insertion may have a higher expulsion rate than delayed insertion. However, these risks may be outweighed by the benefit of immediate contraception.

Emergency contraception over-the-counter: the medical and legal imperatives

Requiring a physician's prescription for hormonal emergency contraceptive pills makes no sense. Unintended pregnancies remain endemic in the United States, and wider use of emergency contraceptive pills could substantially help. However, the prescription requirement poses an unnecessary barrier to prompt, effective use of this preventive therapy. According to the Durham-Humphrey Amendment of 1951, the default option for all new drugs is, in principle, over-the-counter, unless a drug is addictive or dangerous when self-administered. Clearly, hormonal emergency contraception is neither of these. Emergency contraceptive pills meet all the customary criteria for over-the-counter use: low toxicity, no potential for overdose or addiction, no teratogenicity, no need for medical screening, self-identification of the need, uniform dosage, and no important drug interactions. The Food and Drug Administration is authorized, and, by its own regulations, should be required to switch hormonal emergency contraception to over-the-counter status without delay. The current prescription requirement is not only gratuitous but also harmful to women's health because it impedes access to this important therapy.

Lay persons' understanding of the risk of Down's syndrome in genetic counselling

Genetic counselling traditionally expresses risk in proportions (e.g. 1 in 112) rather than as rates (e.g., 8.9 per 1,000). The justification for this practice is unclear. To assess the understanding of lay persons of the risk of Down's Syndrome, whether expressed as rates or as proportions, we analysed 589 self-administered questionnaires. Overall, respondents understood rates significantly better than proportions (76.2% vs 72.3% correct, respectively; P = 0.03) Evidence from two studies in disparate populations suggests that rates are better understood and thus are the preferred way to explain genetic risk to lay persons.

Clinical breast and pelvic examination requirements for hormonal contraception: Current practice vs evidence

Clinical breast and pelvic examinations are commonly accepted practices prior to provision of hormonal contraception. Such examinations, however, may reduce access to highly effective contraceptive methods, and may therefore increase women's overall health risks. These unnecessary requirements also involve ethical considerations and unwittingly reinforce the widely held but incorrect perception that hormonal contraceptive methods are dangerous. This article reviews and summarizes the relevant medical literature and policy statements from major organizations active in the field of contraception. Consensus developed during the last decade supports a change in practice: hormonal contraception can safely be provided based on careful review of medical history and blood pressure measurement. For most women, no further evaluation is necessary. Pelvic and breast examinations and screening for cervical neoplasia and sexually transmitted infection, while important in their own right, do not provide information necessary for identifying women who should avoid hormonal contraceptives or who need further evaluation before making a decision about their use.

Inherited myoclonus-dystonia: evidence supporting genetic heterogeneity

Inherited myoclonus-dystonia (IMD) is a new term used to describe an autosomal dominant form of myoclonus. Recently a family with IMD was linked to a region on chromosome 11q23 and a possible mutation identified in the D2 dopamine receptor. We have identified a large family with 12 affected individuals. Using linkage analysis and direct sequencing, the D2 receptor gene was excluded as a cause of myoclonus in this family. These results indicate that the Val154Ile D2 receptor substitution is not the universal cause of IMD. This suggests either that it is a rare, family specific polymorphism not causative of IMD, or that IMD is genetically heterogeneous.

Evidence-based family planning: the paradigm for the third millennium

Evidence-based medicine applies clinical epidemiology to the care of the individual patient. In contrast, autocratic or authoritarian medicine rests largely on expert opinion and clinical tradition. The need for evidence-based medicine in family planning practice is acute, as counselling for intrauterine devices and tubal sterilization attests. Two international evidence-based guidelines in family planning, both published in 1996, represent a major advance in clinical practice. In addition, the Cochrane Collaboration, a global effort to identify and synthesize randomized controlled trials in medicine, now includes topics on fertility regulation. Evidence-based clinical guidelines and Cochrane systematic reviews are valuable tools for family planning practice. The use of evidence-based medicine will improve clinical care today, and, more importantly, in the millennium which is just beginning.

A faculty development course in obstetrics and gynecology

Sponsored by the nonprofit Berlex Foundation, this 6-day Faculty Development Course introduces small groups of new faculty to research design, critical appraisal of the literature, scientific writing, and evidence-based medicine. The course includes didactic presentations, small group discussions, and individual protocol development. Its influence on academic careers is impossible to determine, because defining an appropriate comparison group is not feasible. However, the cumulative effect should be to increase the research expertise of some young faculty in academic departments nationwide. In addition, many participants have introduced the principles of evidence-based medicine in their own teaching programs.

Intrauterine device and upper-genital-tract infection

Concern about upper-genital-tract infection related to intrauterine devices (IUDs) limits their wider use. In this systematic review I summarise the evidence concerning IUD-associated infection and infertility. Choice of an inappropriate comparison group, overdiagnosis of salpingitis in IUD users, and inability to control for the confounding effects of sexual behaviour have exaggerated the apparent risk. Women with symptomless gonorrhoea or chlamydial infection having an IUD inserted have a higher risk of salpingitis than do uninfected women having an IUD inserted; however, the risk appears similar to that of infected women not having an IUD inserted. A cohort study of HIV-positive women using a copper IUD suggests that there is no significant increase in the risk of complications or viral shedding. Similarly, fair evidence indicates no important effect of IUD use on tubal infertility. Contemporary IUDs rival tubal sterilisation in efficacy and are much safer than previously thought.