Effects of smoking reduction during pregnancy on the birth weight of term infants.

This study was undertaken to determine 1) whether reducing tobacco exposure during pregnancy increases the birth weight of term infants and 2) the relative effects of early- and late-pregnancy exposure to tobacco on infant birth weight. Data were obtained from the Smoking Cessation in Pregnancy project, conducted in public clinics in three states (Colorado, Maryland, and Missouri) between 1987 and 1991. Self-reported cigarette use and urine cotinine concentration were collected from 1,583 pregnant smokers at study enrollment and in the third trimester. General linear models were used to generate mean adjusted birth weights for women who reduced their tobacco exposure by 50 percent or more and for those who did not change their exposure. Regression smoothing techniques were used to characterize the relation between birth weight and early exposure and birth weight and third-trimester exposure. Reducing cigarette use was associated with an increase in mean adjusted birth weight of only 32 g, which was not significant (p = 0.33). As third-trimester cigarette use increased, birth weight declined sharply but leveled off at more than eight cigarettes per day. Findings were similar when urine cotinine concentration was used. Women who smoke during pregnancy may need to reduce to low levels of exposure (less than eight cigarettes per day) to improve infant birth weight.

Measures of maternal tobacco exposure and infant birth weight at term.

This study was undertaken to determine the relation between self-reported number of cigarettes smoked per day and urine cotinine concentration during pregnancy and to examine the relations between these two measures of tobacco exposure and birth weight. Data were obtained from the Smoking Cessation in Pregnancy project, conducted between 1987 and 1991. Cigarette smoking information and urine cotinine concentration were collected for 3,395 self-reported smokers who were receiving prenatal care at public clinics in three US states (Colorado, Maryland, and Missouri) and who delivered term infants. General linear models were used to quantify urine cotinine variability explained by the number of cigarettes smoked per day and to generate mean adjusted birth weights for women with different levels of tobacco exposure. Self-reported number of cigarettes smoked per day explained only 13.9% of the variability in urine cotinine concentration. Birth weight declined as tobacco exposure increased; however, the relation was not linear. The sharpest declines in birth weight occurred at low levels of exposure. Furthermore, urine cotinine concentration did not explain more variability in birth weight than did number of cigarettes smoked. These findings should be considered by researchers studying the effects of smoking reduction on birth outcomes.

Does influenza vaccination prevent asthma exacerbations in children?

OBJECTIVE: Influenza can exacerbate asthma, particularly in children. The effectiveness of influenza vaccine in preventing influenza-related asthma exacerbations, however, is not known. We evaluated influenza vaccine effectiveness in protecting children against influenza-related asthma exacerbations. STUDY DESIGN: We conducted a population-based retrospective cohort study with medical and vaccination records in 4 large health maintenance organizations in the United States during the 1993-1994, 1994-1995, and 1995-1996 influenza seasons. We studied children with asthma who were 1 through 6 years of age and who were identified by search of computerized databases of medical encounters and pharmacy dispensings. Main outcome measures were exacerbations of asthma evaluated in the emergency department or hospital. RESULTS: Unadjusted rates of asthma exacerbations were higher after influenza vaccination than before vaccination. After adjustment was done for asthma severity by means of a self-control method, however, the incidence rate ratios of asthma exacerbations after vaccination were 0.78 (95% CI: 0.55 to 1.10), 0.59 (0.43 to 0.81), and 0.65 (0.52 to 0.80) compared with the period before vaccination during the 3 influenza seasons. CONCLUSIONS: After controlling for asthma severity, we found that influenza vaccination protects against acute asthma exacerbations in children.

Intussusception among infants given an oral rotavirus vaccine.

BACKGROUND: Intussusception is a form of intestinal obstruction in which a segment of the bowel prolapses into a more distal segment. Our investigation began on May 27, 1999, after nine cases of infants who had intussusception after receiving the tetravalent rhesus-human reassortant rotavirus vaccine (RRV-TV) were reported to the Vaccine Adverse Event Reporting System. METHODS: In 19 states, we assessed the potential association between RRV-TV and intussusception among infants at least 1 but less than 12 months old. Infants hospitalized between November 1, 1998, and June 30, 1999, were identified by systematic reviews of medical and radiologic records. Each infant with intussusception was matched according to age with four healthy control infants who had been born at the same hospital as the infant with intussusception. Information on vaccinations was verified by the provider. RESULTS: Data were analyzed for 429 infants with intussusception and 1763 matched controls in a case-control analysis as well as for 432 infants with intussusception in a case-series analysis. Seventy-four of the 429 infants with intussusception (17.2 percent) and 226 of the 1763 controls (12.8 percent) had received RRV-TV (P=0.02). An increased risk of intussusception 3 to 14 days after the first dose of RRV-TV was found in the case-control analysis (adjusted odds ratio, 21.7; 95 percent confidence interval, 9.6 to 48.9). In the case-series analysis, the incidence-rate ratio was 29.4 (95 percent confidence interval, 16.1 to 53.6) for days 3 through 14 after a first dose. There was also an increase in the risk of intussusception after the second dose of the vaccine, but it was smaller than the increase in risk after the first dose. Assuming full implementation of a national program of vaccination with RRV-TV, we estimated that 1 case of intussusception attributable to the vaccine would occur for every 4670 to 9474 infants vaccinated. CONCLUSIONS: The strong association between vaccination with RRV-TV and intussusception among otherwise healthy infants supports the existence of a causal relation. Rotavirus vaccines with an improved safety profile are urgently needed.

[Reactivation of herpes virus infections by vaccination: evidence or coincidence?]. / Reaktivierung von Herpesviren-Infektionen durch Impfungen: Evidenz oder Koinzidenz?

Varicella zoster and herpes simplex viruses cause latent infections by persisting in human cells. Reactivation has been associated with increasing age, immunosuppression, cancer, stress, fever, exposure to ultraviolet light, and tissue damage. Based on three cases reported to the Swiss Drug Monitoring Centre SANZ, we postulated previously that vaccinations may trigger reactivation of herpes virus infections due to vaccine-induced immunomodulation. In the meantime, 10 new cases of reactivated herpes virus infections soon after vaccinations have been reported. They involved 5 women and 5 men with an age range between 16 and 60. In only one case had a trauma preceded, otherwise healthy subjects with no known relevant comorbidity were vaccinated. The clustering of reports after publication points to a previous underreporting of similar cases. This may be explained by the fact that both vaccinations and reactivations of herpes virus infections are frequent, and a causal link is not suspected. However, these new cases do not prove causality, and extensive epidemiological or experimental studies are needed to elucidate the possible link between vaccination and reactivation of herpes virus infections.

Does influenza vaccination exacerbate asthma? Analysis of a large cohort of children with asthma. Vaccine Safety Datalink Team.

CONTEXT: Although influenza vaccination is recommended for children with asthma, only a minority are vaccinated. One reason for low influenza vaccine coverage among children with asthma may be concern that influenza vaccination may induce an exacerbation of asthma. OBJECTIVE: To evaluate the safety of influenza vaccination in children with asthma, we studied the incidence of hospitalizations and emergency department visits for asthma following influenza vaccination. DESIGN: Retrospective cohort study-analysis of population-based computerized medical and vaccination records. SETTING: : Four large health maintenance organizations on the West Coast of the United States. SUBJECTS: Children with asthma 1 through 6 years of age, identified by search of computerized databases of medical encounters and pharmacy prescriptions. MAIN OUTCOME MEASURES: Exacerbations of asthma. RESULTS: In unadjusted analyses vaccination was associated with high rates of asthma exacerbations. However, after adjusting for asthma severity using a self-control method, the incidence rate ratios of asthma exacerbations after vaccination were 0.58 (95% confidence interval, 0.36-0.95), 0.74 (95% confidence interval, 0.47-1.17), and 0.98 (95% confidence interval, 0.76-1.27) during the 3 influenza seasons. CONCLUSIONS: After controlling for asthma severity, we found that influenza vaccination does not result in acute asthma exacerbations in children. Concern about possible exacerbation of asthma is not a valid reason to not vaccinate children with asthma against influenza.

Are interpregnancy intervals between consecutive live births among black women associated with infant birth weight?

OBJECTIVES: The purpose of this study was to determine whether the length of interpregnancy intervals between consecutive live births among Black women had any significant effect on mean birth weight as had previously been reported in another study. DESIGN: We examined a sample (1,048 women, 66% of study participants) from a study of non-Hispanic Black women whose infants were born at a large, inner-city, public hospital in Georgia from October 1988 through August 1990. Data were evaluated for the 494 women whose current and immediately previous pregnancies ended in the birth of a live infant weighing 500 grams or more. METHODS: Linear regression and analysis of covariance models were developed. RESULTS: The median interpregnancy interval was 15 months (range 1 to 207 months), with 19 (4%) of the women having intervals of less than 3 months. After adjustment for parity, gestational age (in weeks), and smoking status, the mean birth weight associated with an interpregnancy interval of three or more months was 3,106 grams, 215 grams greater than that for an interval of less than three months (P = .06). CONCLUSIONS: Although longer birth spacing has been associated with certain positive social and health effects, the population attributable effect on infant birth weight may not be very significant.

Influenza vaccination in children with asthma in health maintenance organizations. Vaccine Safety Datalink Team.

We assessed vaccination coverage and predictors of influenza vaccination in asthmatic children in four large Health Maintenance Organizations. We studied 68,839 children with asthma at four Health Maintenance Organizations (HMOs) in the 1995-1996 influenza season and 34,032 children at two HMOs in the 1996-1997 influenza season. In both seasons only 9-10% were vaccinated against influenza. Children who were hospitalized, had an emergency department visit for asthma or a prescription for a beta-agonist prior to the influenza season, were more likely to be vaccinated. Overall, 61% of the unvaccinated asthmatic children had made an outpatient clinic visit during months when influenza vaccination would have been appropriate. Vaccination coverage could be increased by taking advantage of all opportunities to vaccinate children with asthma whenever they make clinic visits in the fall and early winter.

Immunization levels among premature and low-birth-weight infants and risk factors for delayed up-to-date immunization status. Centers for Disease Control and Prevention Vaccine Safety Datalink Group.

CONTEXT: Studies have noted that health care professionals may not conform to proper immunization schedules for premature and low-birth-weight infants in the United States. Little is known about the success of current efforts to immunize these high-risk infants. OBJECTIVE: To describe current immunization practices for premature and low-birth-weight infants and ascertain risk factors for poor immunization status, using large population-based data sources. DESIGN AND SETTING: Cohort and case-control analyses of immunization data tracked from March 1991 through March 1997 for 3 large health maintenance organizations (HMOs) participating in the Centers for Disease Control and Prevention's Vaccine Safety Datalink project. PARTICIPANTS: A total of 11580 low-birth-weight and premature infants were enrolled from birth to age 2 months; 6832 of these were continuously enrolled from birth to age 24 months. At age 2 months, there were 173373 full-term, normal-birth-weight infants enrolled as controls; at age 24 months, there were 103 324. MAIN OUTCOME MEASURES: Age-specific immunization status by prematurity and birth weight (<1500 g, 1500-2500 g, born at <38 weeks' gestation with birth weight of >2500 g, or full-term with normal birth weight) and patient characteristics associated with up-to-date status. RESULTS: At each age, infants weighing less than 1500 g at birth had lower up-to-date immunization levels than other infants. At age 6 months, 52% to 65% of infants weighing less than 1500 g were up-to-date at each of the 3 HMOs compared with 69% to 73% of those weighing 1500 to 2500 g, 66% to 80% of premature infants weighing more than 2500 g, and 65% to 76% of full-term, normal-birth-weight infants. By age 24 months, 78% to 86% of infants weighing less than 1500 g were up-to-date, significantly less than heavier infants, who had levels of 84% to 89%. Well-child preventive care strongly predicted immunization status, while concomitant pulmonary disease did not. CONCLUSIONS: Our data suggest that infants born prematurely are vaccinated at levels approaching that of the general population, but levels of vaccination for very low-birth-weight infants lag slightly behind.

Maternal cigarette smoking and invasive meningococcal disease: a cohort study among young children in metropolitan Atlanta, 1989-1996.

OBJECTIVES: This study assessed the association between maternal cigarette smoking during pregnancy and the risk of invasive meningococcal disease during early childhood. METHODS: Using a retrospective cohort study design, cases from an active surveillance project monitoring all invasive meningococcal disease in the metropolitan Atlanta area from 1989 to 1995 were merged with linked birth and death certificate data files. Children who had not died or acquired meningococcal disease were assumed to be alive and free of the illness. The Cox proportional hazards analysis was used to assess the independent association between maternal smoking and meningococcal disease. RESULTS: The crude rate of meningococcal disease was 5 times higher for children whose mothers smoked during pregnancy than for children whose mothers did not smoke (0.05% vs 0.01%). Multivariate analysis revealed that maternal smoking (risk ratio [RR] = 2.9; 95% confidence interval [CI] = 1.5, 5.7) and a mother's having fewer than 12 years of education (RR = 2.1; 95% CI = 1.0, 4.2) were independently associated with invasive meningococcal disease. CONCLUSIONS: Maternal smoking, a likely surrogate for tobacco smoke exposure following delivery, appears to be a modifiable risk factor for sporadic meningococcal disease in young children.

Chemical hair treatments and adverse pregnancy outcome among Black women in central North Carolina.

Several studies suggest that toxic chemicals in hair products may be absorbed through the scalp in sufficient amounts to increase the risks of adverse health effects in women or their infants. This case-control study of 525 Black women from three counties in North Carolina who had delivered a singleton, liveborn infant examined whether exposure to chemicals used in hair straightening and curling increased the odds that the infant was preterm or low birth weight. Cases consisted of 188 preterm and 156 low birth weight births (for 123 women, their infant was both low birth weight and preterm). Controls were 304 women who delivered term and normal birth weight infants. Women who used a chemical hair straightener at any time during pregnancy or within 3 months prior to conception had an adjusted odds ratios (OR) of 0.7 (95% confidence interval (CI) 0.4-1.1) for preterm birth and 0.6 (95% CI 0.4-1.1) for low birth weight. Exposure to chemical curl products was also not associated with preterm delivery (adjusted OR = 0.9, 95% CI 0.5-1.8) or low birth weight (adjusted OR = 1.0, 95% CI 0.5-1.9). Despite this failure to find an association, continued search for risk factors to which Black women are uniquely exposed is warranted.

Vasectomy in the United States, 1991 and 1995.

OBJECTIVES: This study sought to assess whether the controversy surrounding publications linking vasectomy and prostate cancer has had an effect on vasectomy acceptance and practice in the United States. METHODS: National probability surveys of urology, general surgery, and family practices were undertaken in 1992 and 1996. RESULTS: Estimates of the total number of vasectomies performed, population rate, and proportion of practices performing vasectomy were not significantly different in 1991 and 1995. CONCLUSIONS: This study provides no solid evidence that the recent controversy over prostate cancer has influenced vasectomy acceptance or practice in the United States. However, the use of vasectomy appears to have leveled off in the 1990s.

Clinical aspects of vasectomies performed in the United States in 1995.

OBJECTIVES: Currently, no surveillance system collects data on the numbers and characteristics of vasectomies performed annually in the United States. This study provides nationwide data on the numbers of vasectomies and the use of no-scalpel vasectomy, various occlusion methods, fascial interposition, and protocols for analyzing semen after vasectomy. METHODS: A retrospective mail survey (with telephone follow-up) was conducted of 1800 urology, family practice, and general surgery practices drawn from the American Medical Association's Physician Master File and stratified by specialty and census region. Mail survey and telephone follow-up yielded an 88% response rate. RESULTS: In 1995, approximately 494,000 vasectomies are estimated to have been performed by 15,800 physicians in the United States. Urologists performed 76% of all vasectomies, and nearly all (93%) urology practices performed vasectomies in 1995. Nearly one third (29%) of vasectomies in 1995 were no-scalpel vasectomies, and 37% of physicians performing no-scalpel vasectomies taught themselves the procedure. The most common occlusion method in 1995 (used for 38% of all vasectomies) was concurrent use of ligation and cautery. In 1995, slightly less than half (48%) of all physicians surveyed interposed the fascial sheath over one end of the vas when performing a vasectomy. Protocols for ensuring azoospermia varied: 56% of physicians required one postvasectomy semen specimen; 39% required two, and 5%, three or more. CONCLUSIONS: No-scalpel vasectomy, used by nearly one third of U.S. physicians, has become an accepted part of urologic care. Physicians' variations in occlusion methods, use of fascial interposition, and postvasectomy protocols underscore the need for large scale, controlled, and statistically valid studies to determine the efficacy of occlusion methods and fascial interposition, as well as whether azoospermia is the only determination of a successful vasectomy.

Trends and predictors of infant sleep positions in Georgia, 1990 to 1995.

BACKGROUND: In recent years, the prone sleeping position has emerged as the strongest modifiable risk factor for sudden infant death syndrome, the leading cause of infant mortality between 1 month and 1 year of age in the United States. Since April 1992, sudden infant death syndrome risk-reduction strategies have included the promotion of the back or side sleeping position (nonprone) for healthy infants younger than 1 year of age. Most recently, the back position has been advocated as the best sleeping position and the side position as an alternative. METHODS: To evaluate trends in prevalence of the prone position from 1990 to 1995, we used data available from the Georgia Women's Health Survey, a random digit-dialed telephone survey of 3130 women 15 to 44 years of age. We examined the position in which women put their infant to sleep in the first 2 months of life for their most recent live birth (N = 868) and determined independent predictors of prone sleep position among women who consistently used the prone or the back/side position (n = 636) using multiple logistic regression. RESULTS: The prevalence of mothers who put their infant to sleep in the prone position significantly decreased, from 49% in 1990 to 15% in 1995. This decrease is primarily attributable to a major shift to the side position rather than to the back. Using multiple logistic regression, we found the prone sleeping position to be significantly higher among women who entered prenatal care after the first trimester (odds ratio [OR], 3.6; 95% confidence interval [CI], 1.4-9.2), were black (OR, 2.1; 95% CI, 1.4-3.1), had less than a high school education (OR, 2.2; 95% CI, 1.4-3.4), and were living in rural Georgia (OR, 1.9; 95% CI, 1.3-2.7). For the period after April 1992, women who had previous children were 2.6 (OR, 95% CI, 1.7-4.1) times more likely to use the prone sleep position than were first-time mothers. CONCLUSIONS: The prevalence of the use of the prone sleep position for infants decreased significantly over the study period. This decrease coincided with national efforts to promote the back or side sleeping position. Increased efforts should target groups who are more likely to use the prone position to attain the national goal of

Multiple induced abortions as risk factor for ectopic pregnancy. A prospective study.

OBJECTIVE: To assess the risk of ectopic pregnancy by the number of previous induced abortions. DESIGN: Prospective cohort study. METHODS: Three thousand seven hundred and fifty-four women, 39 years old or younger, living permanently in one Norwegian county, who had had at least one induced abortion between January 1, 1987 and December 31, 1992, at the University Hospital of Trondheim, Norway were followed prospectively for histologically verified ectopic pregnancies until December 31, 1993. Exposure time was measured from the most recent induced abortion (index abortion) until the ectopic pregnancy, closure date, or the subject's 40th birthday. Statistical analyses were done in SAS applying survival analyses and poisson regression. RESULTS: During the follow-up period of 164,167 women-months, we observed 24 ectopic pregnancies in 3,754 women. The adjusted incidence density ratio (aIDR) for women who had had two or more induced abortions was 1.2 (95% CI: 0.5-3.1) in comparison with the reference group of women who had had one induced abortion. Measuring exposure as increasing number of consecutive induced abortions, no dose-response to ectopic pregnancy was found between two consecutive (aIDR 0.9) and three or more consecutive abortions (aIDR 1.1) in comparison with the reference group. CONCLUSION: In our setting, no excess risk of ectopic pregnancy was associated with multiple previous induced abortions compared with one previous induced abortion.

PIP: To assess the association between induced abortion and subsequent ectopic pregnancy, 3754 Norwegian women 39 years or younger who had at least one induced abortion at the University Hospital of Trondheim during 1987-92 were followed for histologically confirmed ectopic pregnancies through the end of 1993. In a total of 164,167 woman-months of follow-up, 24 ectopic pregnancies were recorded. No woman had more than one ectopic pregnancy. The overall cumulative incidence of ectopic pregnancy among women with an induced abortion history rose from 3.5 per 1000 women at 1 year to 11.1 per 1000 women at 6 years of follow-up. The adjusted incidence density ratio (aIDR) for women with 2 or more induced abortions was 1.2 (95% confidence interval, 0.5-3.1). No dose-response to ectopic pregnancy was found between 2 consecutive (aIDR, 0.9) and 3 or more consecutive (aIDR, 1.1) abortions compared with the reference group. Ectopic pregnancy after the most recent abortion was more likely to occur among women whose first pregnancy ended as an ectopic one than among those whose first pregnancy resulted in a birth. Although the results of longer-term follow-up of this cohort of Norwegian women have not yet been analyzed, the present findings suggest that induced abortion does not increase the risk of ectopic pregnancy.

Vaginal douching and the risk of ectopic pregnancy among black women.

OBJECTIVE: Our goal was to determine whether vaginal douching was associated with ectopic pregnancy among black women and whether specific douching behaviors were associated with differences in risk. STUDY DESIGN: We analyzed data from a case-control study of ectopic pregnancy conducted between October 1988 and August 1990 at a major public hospital in Atlanta, Georgia. Case subjects were 197 black women with surgically confirmed ectopic pregnancies; the control group included 882 black women who were delivered of live or stillborn infants and 237 black women who were seeking to terminate a pregnancy. RESULTS: The adjusted odds ratio for ectopic pregnancy associated with ever having douched was 3.8 (95% confidence interval 1.6 to 8.9). The risk increased with increasing number of years of douching at least once per month. No douching behavior was found to be without risk; even women who douched for routine cleanliness were at increased risk of ectopic pregnancy. CONCLUSIONS: Vaginal douching is a modifiable behavior that may greatly increase a woman's risk of ectopic pregnancy.

Trends in the percentage of women who received no prenatal care in the United States, 1980-1992: contributions of the demographic and risk effects.

OBJECTIVE: To determine if the increase in the percentage of women who received no prenatal care in the United States relative to 1980 (from 1.3% in 1980 to 2.2% in 1989 and 1.7% in 1992) was due to increasing risks of no care in subgroups of women or increasing percentages of births to women at high demographic risk of no care. METHODS: We analyzed U.S. birth certificates for the period 1980-1992. The annual adjusted odds of no prenatal care relative to 1980 were computed by logistic regression models that included year, maternal characteristics, and interactions of these characteristics with year. We also examined changes in the annual distributions of births by maternal characteristics. RESULTS: The risk of no prenatal care in most subgroups increased during the early 1980s, peaked in the late 1980s, and declined thereafter. For example, among black women, the adjusted risk of no care more than doubled from 1980 to 1989. Throughout the 1980s and into the 1990s, the percentage of births to women at high demographic risk of no care increased. This increase in the percentage of births to women at high demographic risk shows no sign of abating. CONCLUSIONS: During the 1980s, increasing risks in subgroups of women drove the increase in the crude rate of no prenatal care. Despite decreases in the risks of no care in the early 1990s, increasing percentages of births to women with high demographic risk for no care prevented a decrease in the crude rate to the 1980 level.

Paraprofessional delivery of a theory based HIV prevention counseling intervention for women.

This report describes a mid-course process evaluation of an HIV risk-reduction counseling intervention delivered by specially trained peer paraprofessionals. One of the key questions addressed is whether paraprofessionals can successfully implement a theory-based counseling intervention. The project, known as Project CARES, is a 5-year demonstration research project to prevent HIV infection and unplanned pregnancies in women at risk for HIV infection and transmission who were recruited from homeless shelters, drug treatment facilities, and hospital-based service settings for HIV-infected women. Project CARES uses an enhanced counseling intervention based on the Transtheoretical Model, also known as the Stages of Change model, to promote condom and other contraceptive use for women who wish to avoid pregnancy, condom use for disease prevention, and reproductive health service use. Peer paraprofessionals, called advocates, provide stage-tailored counseling using a structured manual which guides them in the selection of specific counseling activities appropriate to a woman's level of readiness to change her behavior. Data from process evaluation forms completed by advocates in Philadelphia and Baltimore document that the delivery of the intervention is consistent with the theoretical model upon which it was based. Paraprofessionals can become skilled in the delivery of a stage-based counseling intervention in health and social service settings. The use of paraprofessionals in HIV prevention service delivery may be a cost-effective way to enhance and extend services for women.

Vasectomy in the United States, 1991.

OBJECTIVES: Recent conflicting findings on possible health risks related to vasectomy have underscored the need for reliable and representative estimates of numbers and rates of vasectomies in the United States. The purpose of this study was to estimate the annual US number, rate, and characteristics of vasectomies in 1991. METHODS: A national survey of urology, general surgery, and family practice physician practices was conducted with probability sampling methods (n = 1685 physicians). RESULTS: An estimated 493,487 (95% confidence interval = 450,480, 536,494) vasectomies were performed in 1991, for a rate of 10.3 procedures per 1000 men aged 25 through 49 years. Most vasectomies were performed by urologists, and most were done in physicians' offices with local anesthesia and ligation as the method of occlusion. The rate of vasectomies was highest in the Midwest. CONCLUSIONS: This survey provides the first national estimates of the number and rate of vasectomies in the United States, as well as the first estimates of occlusion method used. Results confirm previous findings that urologists perform most vasectomies and that most vasectomies are performed with local anesthesia. Recommendations include the monitoring of vasectomy numbers and rates as well as demographic studies of men obtaining vasectomies.