Abortion,changed paternity,and risk of preeclampsia in nulliparous women

A prior birth confers a strong protective effect against preeclampsia, whereas a prior abortion confers a weaker protective effect. Parous women who change partners in a subsequent pregnancy appear to lose the protective effect of a prior birth. This study (Calcium for Preeclampsia Prevention Trial, 1992-1995) examines whether nulliparous women with a prior abortion who change partners also lose the protective effect of the prior pregnancy. A cohort analysis was conducted among participants in this large clinical trial of calcium supplementation to prevent preeclampsia. Subjects were nulliparous, had one prior pregnancy or less, delivered after 20 weeks' gestation, and were interviewed at 5-21 weeks about prior pregnancies and paternity. Women without a history of abortion served as the reference group in logistic regression analyses. Women with a history of abortion who conceived again with the same partner had nearly half the risk of preeclampsia (adjusted odds ratio = 0.54, 95 percent confidence interval: 0.31, 0.97). In contrast, women with an abortion history who conceived with a new partner had the same risk of preeclampsia as women without a history of abortion (adjusted odds ratio = 1.03, 95 percent confidence interval: 0.72, 1.47). Thus, the protective effect of a prior abortion operated only among women who conceived again with the same partner. An immune-based etiologic mechanism is proposed, whereby prolonged exposure to fetal antigens from a previous pregnancy protects against preeclampsia in a subsequent pregnancy with the same father.     

Relations of gestational length and timing and type of incomplete pregnancy to ovarian cancer risk

While the protective nature of parity with respect to ovarian cancer has been well documented, whether a history of incomplete pregnancy affects ovarian cancer risk is uncertain. Data collected from 739 epithelial ovarian cancer cases and 1,313 community controls in the Delaware Valley from 1994 to 1998 were used to evaluate the relation between gestational length and timing of first induced or spontaneous abortion and ovarian cancer risk. Incomplete pregnancy was not associated with ovarian cancer among nulliparous women or among ever-pregnant women either before or after adjustment for relevant confounders (for nulliparous women, odds ratio (OR) = 1.12, 95% confidence interval (CI): 0.66, 1.89; for ever-pregnant women, OR = 0.95, 95% CI: 0.76, 1.18). Among unigravid women, one full-term pregnancy was more protective than an incomplete pregnancy (adjusted OR = 0.29, 95% CI: 0.15, 0.57). These results were independent of the type of pregnancy loss. Among ever-pregnant women, a spontaneous abortion before a first birth provided significant protection (adjusted OR = 0.47, 95% CI: 0.30, 0.75), while no significant effect was found for an induced abortion prior to a first birth (adjusted OR = 0.80, 95% CI: 0.44, 1.47). These data do not support an independent association between incomplete pregnancies, either spontaneous or induced, and ovarian cancer risk.     

Prepregnancy body mass index and gestational weight gain as risk factors for preeclampsia and transient hypertension

PURPOSE: Recent studies suggest prepregnancy obesity is a risk factor for preeclampsia, although only a handful of studies have examined the effect of gestational weight gain. The authors analyzed the effect of prepregnancy body mass index (BMI) and weight gain during pregnancy on risk of preeclampsia and transient hypertension.METHODS: Subjects were participants in a prospective cohort study of women who received prenatal care from thirteen obstetric practices in southern Connecticut (4/88-12/91). The women were interviewed in-person before 16 weeks gestation and in the immediate postpartum period. All subjects' hospital delivery charts were abstracted. BMI was categorized as: <19.8 (underweight), 19.8-26 (normal: referent), 26-29 (overweight), >29 (obese). A gestational weight gain index, created using multiple linear regression, compared observed weight gain to the weight gain expected after adjustment for significant covariables (e.g. gestational aged at delivery). Logistic regression was used to estimate risk of preeclampsia (N = 44) and transient hypertension (N = 172) associated with prepregnancy BMI and gestational weight gain.RESULTS: Obese women had a mild increased risk of preeclampsia (OR = 1.81; 0.73-4.52); women in the other BMI categories had risks similar to that of normal BMI subjects. In contrast, risk of transient hypertension was substantially decreased among underweight women (OR = 0.35; 0.14-0.87) and substantially increased among obese women (OR = 3.43; 2.27-5.21). Higher than expected gestational weight gain did not increase the risk of preeclampsia. In contrast, risk of transient hypertension was increased over twofold among women in the highest quartile of the weight gain index (OR = 2.55; 1.66-3.92).CONCLUSIONS: Obesity appears to be a strong risk factor for transient hypertension and a milder risk factor for preeclampsia. High gestational weight gain was associated with increased risk of transient hypertension but not preeclampsia.     

Risk of ectopic pregnancy and previous induced abortion.

OBJECTIVES: This study investigated the role of prior history of induced abortion in subsequent ectopic pregnancies. METHODS: Data from two French case-control studies were used to examine the effect of induced abortion on ectopic pregnancy risk. Case patients (n = 570) were women admitted for ectopic pregnancy during the study period; controls (n = 1385) were women who delivered in the same center. RESULTS: The analysis among women with no previous ectopic pregnancy showed that, after control for the main ectopic pregnancy risk factors, prior induced abortion was associated with an increased risk of ectopic pregnancy (odds ratio [OR] = 1.5, 95% confidence interval [CI] = 1.0, 2.0); there was a significant trend between number of previous induced abortions and ectopic pregnancy risk (ORs = 1.4 for 1 previous induced abortion and 1.9 for 2 or more). CONCLUSIONS: This study suggests that induced abortion may be a risk factor for ectopic pregnancy for women with no previous ectopic pregnancy, particularly in the case of women who have had several induced abortions.     

A prospective study of pregravid oral contraceptive use and risk of hypertensive disorders of pregnancy

Oral contraceptive use is associated with hypertension, dyslipidemias, and insulin resistance, all of which also characterize hypertensive disorders of pregnancy. In this prospective cohort study, the association of oral contraceptive use before pregnancy and the risk of gestational hypertension and preeclampsia was assessed. Between 1991 and 1995, 3973 nulliparous women who reported their first pregnancy lasting > or = 6 months were studied. Pregravid exposures were collected by biennial mailed questionnaires, and cases were confirmed by medical record review. Recent oral contraceptive use was defined as use within 2 years of pregnancy. Proportional hazards analysis was used to adjust for potential confounding variables. During the 4 years of follow-up, 133 (3.3%) women with gestational hypertension and 62 (1.6%) with preeclampsia were identified. Twenty-five percent of women who did not develop these disorders were recent users of oral contraceptives, compared with 19% (p = 0.11) of women who developed gestational hypertension and 30% (p = 0.38) who developed preeclampsia. Mean duration of prior oral contraceptive use was similar for cases and noncases. Compared with never and past users, the multivariate relative risk among recent users for developing gestational hypertension was 0.7 (95% confidence interval (CI), 0.4-1.0) and for preeclampsia was 1.3 (95% CI, 0.8-2.4). Among recent users who had used oral contraceptives for > or = 8 years, the relative risk for gestational hypertension was 0.6 (95% CI, 0.3-1.2) and for preeclampsia was 2.1 (95% CI, 1.1-4.2). When the analysis was restricted to women who had never smoked, the risk for gestational hypertension was 0.2 (95% CI, 0.1-0.9) and for preeclampsia was 4.1 (95% CI, 1.9-8.7). Thus, recent use of oral contraceptives was associated with a reduced risk for developing gestational hypertension. In contrast, there was a suggestion that recent use was associated with an increased risk of developing preeclampsia, but only among women who had used these agents for > or = 8 years.     

Exposure to phenoxy herbicides and the risk of spontaneous abortion.

The Ontario Farm Family Health Study was designed to assess retrospectively the potential adverse effects of exposure to pesticides on pregnancy. Information on the health and life style of approximately 2,000 farm couples, as well as a history of use of pesticides on the farm, was collected by questionnaire. This analysis focuses on pre- and postconception exposure to phenoxy herbicides and the risk of spontaneous abortion using the complete (to date) pregnancy history for each woman. Preconception exposure (from 3 months before conception to the month of conception) was weakly associated with the risk of spontaneous abortion at <20 weeks' gestation [adjusted odds ratio (OR) = 1.1; 95% confidence interval (CI) = 0.6-1.9]. When the analyses were restricted to spontaneous abortions of <12 weeks, the risk was more than doubled (adjusted OR = 2.5; 95% CI = 1.0-6.4), but the results were sensitive to the cutpoint used. If the husband did not normally wear protective equipment during application, the crude OR for early spontaneous abortions was 5.0 (95% CI = 0.7-36.2). Exposure to phenoxy herbicides during the first trimester was generally not associated with increased risk of spontaneous abortion. The results suggest a possible role of preconception (possibly paternal) exposures to phenoxy herbicides in the risk of early spontaneous abortions.     

Low birth weight in relation to multiple induced abortions.

BACKGROUND. Most studies report that a single induced abortion does not increase risk for delivering a low birth weight infant in a subsequent pregnancy. However, the effect of multiple abortions has not been adequately evaluated. METHODS. This relationship was studied in 6541 White women who delivered their first child between 1984 and 1987. We compared the frequencies of low birth weight (less than 2500 g) among infants born to 1999 women without prior induced abortion and 1999 women with one abortion with the frequencies of low birth weight among infants born to women with two (n = 1850), three (n = 520), and four or more (n = 173) prior induced abortions. RESULTS. After adjustment for confounding variables, we found no linear relationship in risk of low birth weight among women with one (relative risk [RR] = 1.2, 95% confidence interval [CI] = 0.9-1.5), two (RR = 1.5, 95% CI = 1.1-2.0), three (RR = 1.3, 95% CI = 0.8-1.9), or four or more (RR = 1.6, 95% CI = 0.9-2.9) prior induced abortions. CONCLUSIONS. These findings confirm earlier reports of little or no evidence of harmful effects on birth weight by one or by two or more induced abortions. We further report that risk is not significantly elevated even in women with three, four, or more prior terminations of pregnancy when compared with women with one or two abortions.     

Prior spontaneous abortion, prior elective termination, interpregnancy interval, and risk of neural tube defects

A woman with a history of spontaneous abortion in her immediately prior pregnancy may be at increased risk for a pregnancy affected by a neural tube defect (NTD). A short interpregnancy interval may further increase this risk. Using data from a population-based case-control study (1989-1991), the authors investigated NTD risk resulting from a prior spontaneous abortion or elective termination and a short interpregnancy interval. Of 538 interviewed case mothers and 539 interviewed control mothers, 408 case mothers and 433 control mothers reported having a prior pregnancy. Analysis showed a slightly decreased NTD risk among mothers whose immediately prior pregnancy had ended in a spontaneous abortion or elective termination in comparison with a live birth (odds ratio (OR) = 0.82; 95% confidence interval (CI): 0.61, 1.1). This decreased risk was consistent across strata of short or long interpregnancy intervals. Additional analysis revealed an increased NTD risk for mothers with an interpregnancy interval of < or =6 months compared with >12-< or =24 months (OR = 1.5; 95% CI: 0.93, 2.4). This latter risk was greatest among mothers whose immediately prior pregnancy had resulted in a live birth (OR = 2.0; 95% CI: 1.0, 3.8) rather than a spontaneous abortion or elective termination (OR = 0.96; 95% CI: 0.44, 2.1). Adjustment for potential covariates did not substantially alter observed risk estimates.     

Spontaneous abortion and work with visual display units.

OBJECTIVE--To determine whether women who work with visual display units are at increased risk of spontaneous abortion. DESIGN--Case-control study. SETTING--Women were recruited during the three years 1987-9 from the Royal Berkshire Hospital in Reading, and from a large group practice situated within the hospital's catchment area. SUBJECTS--Cases were 150 nulliparous working women with a clinically diagnosed spontaneous abortion and controls were 297 nulliparous working women attending for antenatal care. MAIN OUTCOME MEASURES--Cases and controls were contacted and personally interviewed using the same structured questionnaire. Exposure to visual display units (VDUs) at work was assessed from information supplied at interview. RESULTS--No evidence of an increased risk of spontaneous abortion was found in women who reported that they used a VDU at work compared with women who reported that they did not (odds ratio (OR) = 0.9, 95% confidence interval (95% CI) = 0.6-1.4); and no relation with the amount of time spent actively using a VDU was evident (OR = 0.9, 95% CI = 0.5-1.6 for women who worked with a VDU for 21 hours or more each week). No effect of passive exposure to VDUs at work was found (OR = 0.9, 95% CI = 0.6-1.6 for women who reported working less than 10 feet away from a VDU that was usually switched on). These findings were not explained by maternal age, marital state, housing tenure, partner's social class, educational level, smoking, alcohol consumption, or number of previous spontaneous abortions. CONCLUSION--Given the findings and their consistency with the results from other recent studies it is concluded that pregnant women who work with VDUs are not at increased risk of clinically diagnosed spontaneous abortion. For the many women who use VDUs in their jobs, this finding provides reassurance.     

Spontaneous abortion and work with visual display units.

OBJECTIVE--To determine whether women who work with visual display units are at increased risk of spontaneous abortion. DESIGN--Case-control study. SETTING--Women were recruited during the three years 1987-9 from the Royal Berkshire Hospital in Reading, and from a large group practice situated within the hospital's catchment area. SUBJECTS--Cases were 150 nulliparous working women with a clinically diagnosed spontaneous abortion and controls were 297 nulliparous working women attending for antenatal care. MAIN OUTCOME MEASURES--Cases and controls were contacted and personally interviewed using the same structured questionnaire. Exposure to visual display units (VDUs) at work was assessed from information supplied at interview. RESULTS--No evidence of an increased risk of spontaneous abortion was found in women who reported that they used a VDU at work compared with women who reported that they did not (odds ratio (OR) = 0.9, 95% confidence interval (95% CI) = 0.6-1.4); and no relation with the amount of time spent actively using a VDU was evident (OR = 0.9, 95% CI = 0.5-1.6 for women who worked with a VDU for 21 hours or more each week). No effect of passive exposure to VDUs at work was found (OR = 0.9, 95% CI = 0.6-1.6 for women who reported working less than 10 feet away from a VDU that was usually switched on). These findings were not explained by maternal age, marital state, housing tenure, partner's social class, educational level, smoking, alcohol consumption, or number of previous spontaneous abortions. CONCLUSION--Given the findings and their consistency with the results from other recent studies it is concluded that pregnant women who work with VDUs are not at increased risk of clinically diagnosed spontaneous abortion. For the many women who use VDUs in their jobs, this finding provides reassurance.     

Fetal trisomy 21 and maternal preeclampsia

BACKGROUND: Placental trophoblast shedding into maternal circulation has been hypothesized as a potential cause of preeclampsia. Because pregnancies with a trisomy 21 fetus also have high levels of fetal cells and cell-free fetal DNA in maternal circulation, we examined whether trisomy 21 pregnancies have a higher risk of preeclampsia than euploid pregnancies. METHODS: We used 2 population-based databases. We identified 7763 pregnancies with a singleton trisomy 21-affected fetus and 15,293 matched euploid gestations from the U.S. Natality files for the period 1995-1999. The second database consisted of 665 pregnancies with fetal trisomy 21 and 987 euploid controls in a population-based Down syndrome study in California. In the latter study, women were interviewed by telephone regarding characteristics and pregnancy complications. Gestational hypertension and preeclampsia are the outcomes of this study. RESULTS: The U.S. Natality files showed that in nulliparous women fetal trisomy 21 was associated with a reduced risk of pregnancy-induced hypertension (adjusted relative risk [aRR] = 0.67; 95% confidence interval [CI] = 0.53 to 0.85). Findings from the California study confirmed this association in nulliparous women, and further revealed that the decrease in overall risk of pregnancy-induced hypertension was mainly the result of a large reduction in the risk of preeclampsia (aRR = 0.19; CI = 0.04 to 0.88) rather than in gestational hypertension by itself (0.83; 0.37 to 1.84). Neither dataset showed these effects among multiparous pregnancies. CONCLUSION: Fetal trisomy 21 is associated with a reduced, rather than increased, risk of preeclampsia, specifically in nulliparous women.     

Breast cancer in relation to the occurrence and time of induced and spontaneous abortion

The authors evaluated whether an induced or spontaneous abortion during the first six months of gestation, particularly if it occurs before the first term pregnancy, increases the risk of breast cancer. Data from a case-control study of women under 70 years of age were used: 3,200 cases of breast cancer were compared with 4,844 controls with nonmalignant nongynecologic conditions. Among both nulliparous and parous women, the risk of breast cancer was not related to the number of induced or spontaneous abortions. After allowance for all identified potential confounding factors, the estimated relative risk for nulliparous women with an induced abortion relative to those who had never been pregnant was 1.3 (95% confidence interval (CI) 0.8-2.2), and for spontaneous abortion, the corresponding estimate was 0.9 (95% CI 0.5-1.5). Among parous women, the estimated relative risks were 1.2 (95% CI 0.9-1.6) for an induced abortion and 0.9 (95% CI 0.8-1.0) for a spontaneous abortion, relative to never having had an abortion of any type. The time of the abortion had little effect: The relative risk estimates were 0.9 (95% CI 0.5-1.4) for induced abortion before the first term birth, 1.4 (95% CI 1.0-1.9) for induced abortion first occurring after the first term birth, 0.9 (95% CI 0.7-1.2) for spontaneous abortion before the first term birth, and 0.9 (95% CI 0.7-1.0) for spontaneous abortion first occurring after the first term birth. Similar results were evident for women under age 40, among whom the frequency of induced abortion was relatively high. These data suggest that the risk of breast cancer is not materially affected by abortion, regardless of whether it occurs before or after the first term birth.     

Unintended pregnancy and its risk factors among university students in eastern China

BACKGROUND: The study was conducted to determine the prevalence of unintended pregnancy, induced abortion and contraceptive use, and factors associated with unintended pregnancy among Chinese university students. STUDY DESIGN: A self-administered questionnaire survey with cross-sectional design was administered among students in two universities in Ningbo, China, in November-December 2003. Sociodemographic and behavioral factors associated with unintended pregnancy were identified in both genders using univariate and multivariate analyses. RESULTS: Of sexually active students, 10.6% of male and 11.6% of female students reported their partner or they had a history of pregnancy; 10.0% of male and 11.3% of female students reported their partner or they had a history of induced abortion. The risk factors for unintended pregnancy identified among males by multivariate analysis were older age [odds ratio (OR), 2.12; 95% confidence interval (CI), 1.15-3.88], initiation of sexual activity before high school (OR, 2.45; 95% CI, 1.36-4.44), reported lack of condom use in first sexual activity (OR, 1.71; 95% CI, 1.10-2.64), multiple sexual partners (OR, 1.54; 95% CI, 1.06-2.23), and often used condoms during their lifetime (OR, 1.97; 95% CI, 1.01-3.81). The identified risk factors among females were initiation of sexual activity before high school (OR, 5.12; 95% CI, 1.49-17.68), non-consensual sexual intercourse as first sex (OR, 1.77; 95% CI, 1.08-2.90), multiple partners (OR, 2.75; 95% CI, 1.61-4.71), and sometimes/never (OR, 3.02; 95% CI, 1.16-7.87) or often (OR, 3.92; 95% CI, 1.43-10.73) used condoms during their lifetime. CONCLUSION: The high prevalence of unintended pregnancies and induced abortions in this population indicates a need for better and targeted sex education and family planning services.     

Risk factors for uterine fibroids among women undergoing tubal sterilization

Uterine leiomyomas are reported to be the most common benign gynecologic tumors affecting premenopausal women, and they are often associated with considerable morbidity. The purpose of this study was to identify risk factors for uterine fibroids among women undergoing tubal sterilization. Cases comprised women aged 17-44 years whose uterine fibroids were first visualized at the time of tubal sterilization (1978-1979 or 1985-1987) or who reported a history of uterine fibroids (n = 317). Controls were randomly selected from women with no laparoscopic evidence of or history of fibroids (n = 1,268). Adjusted odds ratios were estimated using unconditional logistic regression separately for White (n = 1,235) and African-American (n = 350) women. Risk factors for White women included: age 40-44 years (odds ratio (OR) = 6.3; 95% confidence interval (CI): 3.5, 11.6), > or =5 years since last delivery (OR = 1.9; 95% CI: 1.1, 3.1), lifetime cigarette smoking of > or =1 pack/day (OR = 1.6; 95% CI: 1.1, 2.3), menstrual cycle length of >30 days (OR = 1.6; 95% CI: 1.1, 3.3), and menstrual bleeding for > or =6 days (OR = 1.4; 95% CI: 1.0, 2.0). Parous women were at reduced risk compared with nulliparous women (OR = 0.2; 95% CI: 0.1, 0.3). Advancing age was the only significant risk factor for African-American women (ages 40-44 years, OR = 27.5; 95% CI: 5.6, 83.6). Current oral contraceptive use and elective abortion were not associated with fibroids.     

Work, leisure-time physical activity, and risk of preeclampsia and gestational hypertension

Few studies of preeclampsia have assessed physical activity level, yet recent evidence suggests that the pathologic mechanisms in preeclampsia are similar to those in cardiovascular disease, for which physical activity is shown to be protective. The authors assessed the independent and combined effects of work and regular leisure-time physical activity (LTPA) during early pregnancy on risk of de novo preeclampsia (n = 44) and gestational hypertension (n = 172) among women recruited from 13 obstetric practices in the New Haven, Connecticut, area between 1988 and 1991. Control subjects were normotensive throughout pregnancy (n = 2,422). Information on time at work spent sitting, standing, and walking and on LTPA before and during pregnancy was collected via face-to-face interviews. Logistic regression analyses suggested that women who engaged in any regular LTPA regardless of caloric expenditure (adjusted odds ratio (aOR) = 0.66, 95% confidence interval (CI): 0.35, 1.22), were unemployed (aOR = 0.64, 95% CI: 0.21, 2.00), or had nonsedentary jobs (aOR = 0.71, 95% CI: 0.37, 1.36) were at decreased risk of preeclampsia. Analyses of gestational hypertension showed no indication of a protective effect of workplace activity, LTPA, or unemployment. Consistent with other studies, these data suggest that regular physical activity during pregnancy may reduce preeclampsia risk.     

The effect of cigarette smoking on the risk of preeclampsia and gestational hypertension

This case-control study assessed the relation of cigarette smoking during pregnancy to the risk of preeclampsia and gestational hypertension. All subjects were primiparous women without a history of high blood pressure who gave birth in Quebec City or Montreal, Canada, hospitals between 1984 and 1986. Cases (172 women with preeclampsia and 251 with gestational hypertension) and 505 controls were interviewed at the hospital after delivery. Adjusted relative risks were estimated by polychotomous logistic regression. Compared with women who had never smoked, women who were smokers at the onset of pregnancy had a reduced risk of preeclampsia (relative risk = 0.51, 95% confidence interval 0.34-0.77). Relative risks of preeclampsia decreased with increases in the number of cigarettes smoked daily at the onset of pregnancy: Relative risks among smokers of less than 11, 11-20, and more than 20 cigarettes per day were 0.79, 0.56, and 0.38, respectively (test for trend: p = 0.0002). The protective effect of smoking on preeclampsia was stronger for women who continued to smoke after 20 weeks of pregnancy. While smoking tended to reduce the risk of gestational hypertension, this effect was less evident than that for preeclampsia. Relative risks varied little with severity of disease as based on gestational age at the onset of hypertension, maximal blood pressure and, for preeclampsia, amount of proteinuria. The reduction in mean birth weight attributable to smoking during pregnancy was similar among cases and controls. Nicotine inhibition of thromboxane A2 production might explain the decreased risk of pregnancy-induced hypertension among smokers. Despite these findings, the harmful consequences of smoking on pregnancy outcome outweigh its protective effect against pregnancy-induced hypertension.     

Mifepristone-induced abortion and vaginal bleeding in subsequent pregnancy

BackgroundThe aim of this study is to explore the effect of first-trimester mifepristone-induced abortion on vaginal bleeding in subsequent pregnancy.Study DesignThis observational cohort study was conducted during 1998–2001 at antenatal clinics in Beijing, Chengdu, and Shanghai, China. The study enrolled 4,931 women with one previous mifepristone-induced abortion, 4,925 women with no history of induced abortion, and 4,800 women with one previous surgical abortion and followed them through pregnancy and childbirth.ResultsThe rates of vaginal bleeding in pregnant women with a history of medical abortion, no abortion, and surgical abortion were 16.5%, 13.9%, and 17.3%, respectively. The women with medical abortion had a higher risk (adjusted relative risk (aRR)=1.17, 95% confidence interval (CI): 1.07, 1.29) of vaginal bleeding compared with those with no abortion but similar risk to prior surgical abortion. When the correlation between medical abortion and vaginal bleeding was examined by period, increased risk was observed only in the early period (<16 gestational weeks) (aRR=1.25, 95% CI: 1.12, 1.39). The comparison between subgroups of medical abortion and no abortion showed that the observed risks increased particularly in those with abortion at gestational age ≤7 weeks (aRR=1.33, 95% CI: 1.18, 1.49), those followed by a postabortion curettage (aRR=1.58, 95% CI: 1.37, 1.84) or complications (aRR=1.99, 95% CI: 1.67, 2.37). There was no difference between women with medical abortion and women with surgical abortion in the occurrence of vaginal bleeding for either period.ConclusionsOne previous mifepristone-induced abortion increased the risk of vaginal bleeding in early gestation period of subsequent pregnancy compared with no abortion, especially if abortion occurred before 7 weeks of gestation and was followed by a curettage or complications.     

夫妻生活习惯与不良生育史的关系

目的调查西城区育龄妇女不良生育史的发生情况及与夫妻双方生活习惯的关系,为优生优育工作提供依据。方法采用横断面调查,对2005—2009年北京市西城区12191位有生育意愿育龄妇女的不良生育史,夫妻双方生活习惯、危险因素接触及患病情况等进行分析,探讨影响不良生育史发生的因素。结果研究人群的不良生育史发生比例为2．1％,其中自然流产史发生比例为1．6％;妻子挑食,丈夫吸烟、饮酒者自然流产史发生比例高;夫妻至少一方接触毒物,妻子挑食,丈夫饮酒者死胎死产史发生比例高;夫妻至少一方吸烟,丈夫接触毒物者宫外孕史发生比例高,与无上述因素者比较,差异有统计学意义;Logistic回归结果显示,妻子挑食（OR=1．2,95％CI：1．0～1．4）、丈夫吸烟（OR=2．0,95％CI：1．4—2．8）者发生自然流产史的风险高;妻子挑食（OR=1．2,95％CI：1．0—1．4）、丈夫饮酒（OR=2．0,95％CI：1．4～2．8）、丈夫接触毒物（OR=6．3,95％CI：2．3—17．3）者发生不良生育史风险高。结论不良生育史的发生与夫妻生活习惯有关,预防不良生殖结局的发生应将夫妻双方均作为目标人群进行干预。     

Marijuana and spontaneous abortion of known karyotype

We tested whether marijuana use in the 2 months before the last menstrual period and during pregnancy affects the risk of spontaneous abortions of known karyotype. Spontaneous abortions (cases) were defined as chromosomally normal (n = 567) or chromosomally aberrant (n = 393) and, within the latter, by type of aberration (212 trisomies, 71 monosomies X, 49 triploidies, 61 others). Controls were women with prenatal care before 22 weeks gestation and delivering at 28 weeks or later (n = 2042). In comparison with controls, adjusted odds (OR) of reported marijuana use in chromosomally normal cases were 1.1 (95% confidence interval (CI) 0.7, 1.5) and in chromosomally aberrant cases combined 1.2 (95% CI 0.7, 1.9). With respect to specific aberrations, use in the perifertilisation period did not differ significantly from that in controls for trisomies (adjusted OR = 0.8, 95% CI 0.4, 1.8), monosomies X (adjusted OR = 1.8, 95% CI 0.7, 4.3), and triploidies (adjusted OR = 1.3, 95% CI 0.4, 4.5). Comparison of karyotype groups with each other yielded similar results. Our data do not support causal associations of marijuana use, at the levels represented in our sample, with either chromosomally normal or trisomic spontaneous abortion. With monosomy X and triploidy, no statistically significant associations were detected although numbers were insufficient to rule out moderate effects.     

The use of electric bed heaters and the risk of clinically recognized spontaneous abortion

We conducted a prospective cohort study to evaluate the relation of spontaneous abortion and electric bed heater use during the first trimester of pregnancy. Compared with non-users, rates of spontaneous abortion were lower for women who used electric bed heaters. The adjusted odds ratio and 95% confidence interval (CI) for the two major devices used, electric blankets (N = 524) and waterbeds (N = 796), were, respectively, 0.8 (95% CI = 0.5-1.1) and 0.9 (95% CI = 0.7-1.2). An increase of risk with increasing intensity (setting-duration combination) of use was not observed. Users of electric blankets at low settings for most of the night (N = 171) had lower risks of spontaneous abortion than non-users (adjusted odds ratio = 0.5; 95% CI = 0.3-1.0). Twenty women who used electric blankets at a high setting for 1 hour or less had an adjusted odds ratio of 3.0 (95% CI = 1.1-8.3), but we found no spontaneous abortions among the few women (N = 13) who used a high setting for 2 or more hours. We found that exposure rankings of the magnetic field time-weighted average and a rate of change metric did not correspond monotonically to the pattern of spontaneous abortion risks and that electric blankets contribute less to overnight time-weighted average magnetic fields than has been thought.