PUBLIC HEALTH BRIEFS
Prior Cesarean Delivery in Women with Secondary Tubal Infertility MARSHA E. WOLF, PHD, JANET R. DALING, PHD, Abstract: The history of cesarean delivery was evaluated in a population-based case-control study of secondary infertility in King County, Washington. Sixty-one married women diagnosed with secondary infertility due to tubal problems who had a previous viable pregnancy were compared to 343 married women who had a previous viable pregnancy and then had a live birth that was conceived at the same time the infertile women began trying to conceive. The risk of tubal infertility was not substantially elevated in women who had a previous cesarean delivery in the most recent viable pregnancy compared to women with vaginal delivery (odds ratio = 1.2; 95% confidence interval = 0.4, 3.7). (Am J Public Health 1990; 80:13821383.)
Introduction Cesarean section deliveries in the United States have increased from 5.5 per 100 deliveries in 1970 to 20.3 in 1983.1,2 Women who have cesarean deliveries are at greater risk for postpartum complications of pelvic infections than women who deliver vaginally,3 but the effect of cesarean delivery and related postpartum infection on subsequent fertility is not well understood.4-'0
Methods A case-control study design was used, in which the cases were 61 20-39 year old married women residents of King County, Washington who had secondary infertility (women who had previously conceived, but who were not able to conceive after trying for at least one year) and who have previously delivered a live birth or still birth. These women had their first medical evaluation for infertility during 1979 to 1981. (The study subjects were part of a larger study on infertility and contraception in which 89.5 percent of all physicians in King County who perform infertility evaluations agreed to participate.)" If cesarean section via a possible infection did lead to infertility in some women, it would more likely be women whose infertility was related to a tubal condition.'2,13 For this reason only women with blocked tubes, diagnosed by hysterosalpingogram or surgery, were included as cases. Women with an abnormal hysterosalpingogram who were later found by surgery to have an intrauterine abnormality, rather than a tubal condition, were excluded. The control group (n = 343), identified from state vital records, was composed of 20-39 year old married women residents of King County who had a previous birth and then subsequently delivered a newborn who was conceived during From the Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle (all authors); the Harborview Injury Prevention and Research Center (Wolf); and the Fred Hutchinson Cancer Research Center, Division of Public Health Sciences (Daling, Voigt). Address reprint requests to Marsha E. Wolf, PhD, Harborview Injury Prevention and Research Center, 325 Ninth Avenue, Mailstop ZX-10, Seattle, WA 98104. This paper, submitted to the Journal October 24, 1988, was revised and accepted for publication March 20, 1990. C 1990 American Journal of Public Health 0090-0036/90$1.50
1382
AND
LYNDA F. VOIGT, PHD
the same years in which the infertile cases started trying to become pregnant. By structured interview, data for each study subject were collected on demographic characteristics, use of "social" drugs, tobacco, alcohol, personal hygiene, and medical, reproductive, contraceptive, and sexual histories. Results
Although cases and controls were somewhat similar with regard to education, income, and age at reference date (the time at which both the infertile case and the control began to attempt to conceive), the cases had a larger percentage of racial minorities and were more likely to have been employed, to be a smoker, and to have had more sexual partners, a history of Dalkon Shield use, and their last viable pregnancy before 1975 than did the controls (Table 1). A cesarean section delivery of the most recent birth was found in four cases (6.6 percent) and in 29 controls (8.3 percent). Using unconditional logistic regression to obtain maximum likelihood estimates of relative risk, we adjusted for the effects of age (less than 30, 30 or older) and year of last viable pregnancy (before 1975, 1975 or after). The adjusted odds ratio, an estimate of the relative risk, was 1.2 (95 percent confidence interval = 0.4, 3.7). Since the number of exposed cases was small, we also performed exact stratified analysis with EGRET statistical software which utilizes the method described by Mehta, Patel and Gray.14 The exact odds ratio, adjusted for the same variables as above had slightly wider confidence intervals (OR = 1.2; 95% CI = 0.3, 3.8). Variables that were assessed but did not appreciably change the cesarean delivery risk estimates included race, employment type, smoking status, parity, education, income, age at first coitus, number of lifetime sexual partners, history of Dalkon Shield and other intrauterine device use, history of gonorrhea, pelvic inflammatory disease, douching, marijuana use, and census tract of residence. In our study, no case or control with a cesarean delivery reported postpartum pelvic infection. Discussion
Although this study revealed no association between cesarean delivery and subsequent secondary tubal infertility, the small sample size limited the study's ability to detect a possible modest increase in risk associated with cesarean delivery. The 95% CI suggests a relative risk of 3.7 or more is highly unlikely. Another limitation of the data is that women with a prior successful pregnancy who had a cesarean delivery may be less motivated to seek help or to undergo the expense or discomfort of invasive techniques, i.e. hysterosalpingogram or laparoscopic surgery necessary to diagnose tubal infertility. To the extent this is so, ascertainment of cases of women with secondary tubal infertility among women with cesarean section will be incomplete, and the observed risk will underestimate the true risk. Finally, we were unable to assess the more direct measure of post-cesarean pelvic infection itself, except by self-report. Medical charts were not reviewed. AJPH November 1990, Vol. 80, No 11
PUBLIC HEALTH BRIEFS Table 1-Characteristics of Women with Secondary Tubal Infertility and Controls
Cases Characteristic (at reference date) Education
Prior Cesarean Delivery in Women with Secondary Tubal Infertility MARSHA E. WOLF, PHD, JANET R. DALING, PHD, Abstract: The history of cesarean delivery was evaluated in a population-based case-control study of secondary infertility in King County, Washington. Sixty-one married women diagnosed with secondary infertility due to tubal problems who had a previous viable pregnancy were compared to 343 married women who had a previous viable pregnancy and then had a live birth that was conceived at the same time the infertile women began trying to conceive. The risk of tubal infertility was not substantially elevated in women who had a previous cesarean delivery in the most recent viable pregnancy compared to women with vaginal delivery (odds ratio = 1.2; 95% confidence interval = 0.4, 3.7). (Am J Public Health 1990; 80:13821383.)
Introduction Cesarean section deliveries in the United States have increased from 5.5 per 100 deliveries in 1970 to 20.3 in 1983.1,2 Women who have cesarean deliveries are at greater risk for postpartum complications of pelvic infections than women who deliver vaginally,3 but the effect of cesarean delivery and related postpartum infection on subsequent fertility is not well understood.4-'0
Methods A case-control study design was used, in which the cases were 61 20-39 year old married women residents of King County, Washington who had secondary infertility (women who had previously conceived, but who were not able to conceive after trying for at least one year) and who have previously delivered a live birth or still birth. These women had their first medical evaluation for infertility during 1979 to 1981. (The study subjects were part of a larger study on infertility and contraception in which 89.5 percent of all physicians in King County who perform infertility evaluations agreed to participate.)" If cesarean section via a possible infection did lead to infertility in some women, it would more likely be women whose infertility was related to a tubal condition.'2,13 For this reason only women with blocked tubes, diagnosed by hysterosalpingogram or surgery, were included as cases. Women with an abnormal hysterosalpingogram who were later found by surgery to have an intrauterine abnormality, rather than a tubal condition, were excluded. The control group (n = 343), identified from state vital records, was composed of 20-39 year old married women residents of King County who had a previous birth and then subsequently delivered a newborn who was conceived during From the Department of Epidemiology, School of Public Health and Community Medicine, University of Washington, Seattle (all authors); the Harborview Injury Prevention and Research Center (Wolf); and the Fred Hutchinson Cancer Research Center, Division of Public Health Sciences (Daling, Voigt). Address reprint requests to Marsha E. Wolf, PhD, Harborview Injury Prevention and Research Center, 325 Ninth Avenue, Mailstop ZX-10, Seattle, WA 98104. This paper, submitted to the Journal October 24, 1988, was revised and accepted for publication March 20, 1990. C 1990 American Journal of Public Health 0090-0036/90$1.50
1382
AND
LYNDA F. VOIGT, PHD
the same years in which the infertile cases started trying to become pregnant. By structured interview, data for each study subject were collected on demographic characteristics, use of "social" drugs, tobacco, alcohol, personal hygiene, and medical, reproductive, contraceptive, and sexual histories. Results
Although cases and controls were somewhat similar with regard to education, income, and age at reference date (the time at which both the infertile case and the control began to attempt to conceive), the cases had a larger percentage of racial minorities and were more likely to have been employed, to be a smoker, and to have had more sexual partners, a history of Dalkon Shield use, and their last viable pregnancy before 1975 than did the controls (Table 1). A cesarean section delivery of the most recent birth was found in four cases (6.6 percent) and in 29 controls (8.3 percent). Using unconditional logistic regression to obtain maximum likelihood estimates of relative risk, we adjusted for the effects of age (less than 30, 30 or older) and year of last viable pregnancy (before 1975, 1975 or after). The adjusted odds ratio, an estimate of the relative risk, was 1.2 (95 percent confidence interval = 0.4, 3.7). Since the number of exposed cases was small, we also performed exact stratified analysis with EGRET statistical software which utilizes the method described by Mehta, Patel and Gray.14 The exact odds ratio, adjusted for the same variables as above had slightly wider confidence intervals (OR = 1.2; 95% CI = 0.3, 3.8). Variables that were assessed but did not appreciably change the cesarean delivery risk estimates included race, employment type, smoking status, parity, education, income, age at first coitus, number of lifetime sexual partners, history of Dalkon Shield and other intrauterine device use, history of gonorrhea, pelvic inflammatory disease, douching, marijuana use, and census tract of residence. In our study, no case or control with a cesarean delivery reported postpartum pelvic infection. Discussion
Although this study revealed no association between cesarean delivery and subsequent secondary tubal infertility, the small sample size limited the study's ability to detect a possible modest increase in risk associated with cesarean delivery. The 95% CI suggests a relative risk of 3.7 or more is highly unlikely. Another limitation of the data is that women with a prior successful pregnancy who had a cesarean delivery may be less motivated to seek help or to undergo the expense or discomfort of invasive techniques, i.e. hysterosalpingogram or laparoscopic surgery necessary to diagnose tubal infertility. To the extent this is so, ascertainment of cases of women with secondary tubal infertility among women with cesarean section will be incomplete, and the observed risk will underestimate the true risk. Finally, we were unable to assess the more direct measure of post-cesarean pelvic infection itself, except by self-report. Medical charts were not reviewed. AJPH November 1990, Vol. 80, No 11
PUBLIC HEALTH BRIEFS Table 1-Characteristics of Women with Secondary Tubal Infertility and Controls
Cases Characteristic (at reference date) Education
