Induced abortion: not an independent risk factor for pregnancy outcome, but a challenge for health counseling

PURPOSE: Low birth weight (LBW), preterm births, abnormal placentation, and miscarriages have been associated with prior induced abortions. An incidence-related effect has been suggested. The objective of this study is to assess the effects of prior induced abortions on obstetric risk factors and pregnancy outcome in conditions of free high-standard maternity care used by almost the entire pregnant population in Finland. METHODS: We analyzed a population-based database including 26,976 singleton pregnancies from 1989 to 2001, of which 2364 were among women with one prior induced abortion and 355 women had had at least two prior induced abortions. Data included maternal risk factors, pregnancy characteristics, and obstetric outcome measures and were based on results of a self-administered questionnaire at 20 weeks of pregnancy and clinical records. Odds ratios (ORs) concerning pregnancy outcomes were calculated in multiple logistic regression analysis. RESULTS: Induced abortions were associated with several known pregnancy risk factors; specifically, maternal age older than 35 years, unemployment, unmarried status, low educational level, smoking, alcohol consumption, overweight condition, and chronic illnesses. Preterm birth (OR, 1.19; 95% confidence interval, 1.01-1.41) in women with one prior abortion (7.3% versus 6.2%) and LBW (OR, 1.54; 95% confidence interval, 1.02-2.32) in women with two or more prior abortions (7.0% versus 4.7%) appeared to be more common, but after logistic regression analysis, we found no evidence of adverse pregnancy outcomes. CONCLUSIONS: Induced abortion is not an independent risk factor for adverse obstetric outcome. Marked health behavioral pregnancy risks are associated with prior induced abortions. Health counseling of these women is a challenge, but this objective has not yet been achieved.     

Vaginal bleeding during pregnancy and preterm birth

This study investigated the relation between self-reported vaginal bleeding during pregnancy and preterm birth in a prospective cohort of 2,829 pregnant women enrolled from prenatal clinics between 1995 and 2000 in central North Carolina. The overall association between vaginal bleeding and preterm birth was modest (risk ratio (RR) = 1.3, 95% confidence interval (CI): 1.1, 1.6). Bleeding in the first trimester only was associated with earlier preterm birth (< or =34 weeks' gestation) (RR = 1.6, 95% CI: 1.1, 2.4) and preterm birth due to preterm premature rupture of the membranes (PPROM) (RR = 1.9, 95% CI: 1.1, 3.3). Bleeding in both trimesters was associated with preterm birth due to preterm labor (RR = 3.6, 95% CI: 1.9, 6.8). Bleeding of multiple episodes, on multiple days, and with more total blood loss was associated with an approximate twofold increased risk of earlier preterm birth, PPROM, and preterm labor. In contrast, bleeding in the second trimester only, of a single episode, on a single day, and with less total blood loss was not associated with any category of preterm birth. Vaginal bleeding was not associated with preterm birth among African Amercians (RR = 1.2, 95% CI: 0.9, 1.7). This study indicates that more intense but not less intense bleeding is associated with earlier preterm birth and spontaneous preterm birth presenting as PPROM or preterm labor, and it suggests that bleeding is less predictive of preterm birth among African-American compared with White women.     

Modelling prior reproductive history to improve prediction of risk for very preterm birth

Watson LF, Rayner J‐A, King J, Jolley D, Forster D, Lumley J. Modelling prior reproductive history to improve prediction of risk for very preterm birth. Paediatric and Perinatal Epidemiology 2010. In published studies of preterm birth, analyses have usually been centred on individual reproductive events and do not account for the joint distributions of these events. In particular, spontaneous and induced abortions have often been studied separately and have been variously reported as having no increased risk, increased risk or different risks for subsequent preterm birth. In order to address this inconsistency, we categorised women into mutually exclusive groups according to their reproductive history, and explored the range of risks associated with different reproductive histories and assessed similarities of risks between different pregnancy histories. The data were from a population‐based case–control study, conducted in Victoria, Australia. The study recruited women giving birth between April 2002 and April 2004 from 73 maternity hospitals. Detailed reproductive histories were collected by interview a few weeks after the birth. The cases were 603 women who had had a singleton birth between 20 and less than 32 weeks gestation (very preterm births including terminations of pregnancy) and the controls were 796 randomly selected women from the population who had had a singleton birth of at least 37 completed weeks gestation. All birth outcomes were included. Unconditional logistic regression was used to assess the association of very preterm birth with type and number of prior abortions, prior preterm births and sociodemographic factors. Using the complex combinations of prior pregnancy experiences of women (including nulligravidity), we showed that a history of prior childbirth (at term) with no preterm births gave the lowest risk of very preterm birth. With this group as the reference category, odds ratios of more than two were associated with all other prior reproductive histories. There was no evidence of difference in risk between types of abortion (i.e. spontaneous or induced) although the risk increased if a prior preterm birth had also occurred. There was an increasing risk of very preterm birth associated with increasing numbers of abortions. This method of data analysis reveals consistent and similar risks for very preterm birth following spontaneous or induced abortions. The findings point to the need to explore commonalities rather than differences in regard to the impact of abortion on subsequent births.     

Gestational vaginal bleeding and pregnancy outcome

The relation between vaginal bleeding and pregnancy outcome was examined in a prospective study of 3,531 women seeking prenatal care in New York City from 1975 through 1985. Women were interviewed in the second trimester or later and were followed up at delivery. The frequency of vaginal bleeding during pregnancy was 22%. Few maternal characteristics or exposures were predictive of bleeding, and those that were associated with an increased risk of bleeding were only marginally so. Risk factors included advanced maternal age, previous spontaneous or induced abortion, working during pregnancy, and certain gynecologic conditions (fibroids, cervical inflammation, and ovarian cysts). Severity of bleeding was examined in relation to birth weight and length of gestation at delivery. Light bleeding during pregnancy was not associated with decreased birth weight or with shortened gestation at delivery. Heavy bleeding was associated with a decrease in mean birth weight of about 100 g (p less than 0.05) but was not significantly associated with the risk of low birth weight (odds ratio (OR) = 1.7, 95% confidence interval (CI) 0.9-3.3). Heavy bleeding was associated with preterm delivery among private patients (OR = 6.4, 95% Cl 1.7-23.5) but not public patients (OR = 0.3, 95% Cl 0.1-1.4). First trimester bleeding of any severity was marginally associated with congenital malformations in the offspring (OR = 1.7, 95% Cl 1.0-2.9); the effect was the same for major and minor abnormalities. There was no association between first trimester bleeding and placental complications of pregnancy or the delivery of a stillborn infant.     

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.     

Modelling sequence of prior pregnancies on subsequent risk of very preterm birth

Watson LF, Rayner J‐A, King J, Jolley D, Forster D, Lumley J. Modelling sequence of prior pregnancies on subsequent risk of very preterm birth. Paediatric and Perinatal Epidemiology 2010. The prevalence and intractability of preterm birth is known as is its association with reproductive history, but the relationship with sequence of pregnancies is not well studied. The data were from a population‐based case–control study, conducted in Victoria, Australia. The study recruited women giving birth between April 2002 and April 2004 from 73 maternity hospitals. Detailed reproductive histories were collected by interview a few weeks after the birth. The cases were 603 women having a singleton birth between 20 and <32 weeks gestation (very preterm births including terminations of pregnancy). The controls were 796 randomly selected women from the population having a singleton birth of at least 37 completed weeks gestation. Unconditional logistic regression was used to assess the association of very preterm birth with sequence of pregnancies defined by their outcome (prior abortion – spontaneous or induced, and prior preterm or term birth) with adjustment for sociodemographic factors. The outcomes of each prior pregnancy, stratified by pregnancy order, and starting with the pregnancy immediately before the index or control pregnancy, were categorised as one of abortion, preterm birth or term birth. We showed that each of these prior pregnancy events was an independent risk of very preterm birth. This finding does not support the hypothesis of a neutralising effect of a term birth after an abortion on the subsequent risk for very preterm birth and is further evidence for the cumulative or increasing risk associated with increasing numbers of prior abortions or preterm births.     

Risk factors for spontaneous preterm birth among Aboriginal and non-Aboriginal women in Manitoba

In the province of Manitoba, the incidence of preterm birth has been increasing and the rate is higher among Aboriginal than non-Aboriginal women. The purpose of this study was to identify risk factors for spontaneous preterm birth in Manitoba women, and to compare risk factors among Aboriginal and non-Aboriginal women. A case-control study was performed at two tertiary care hospitals in Winnipeg, Manitoba, Canada from October 1999 to December 2000. Cases delivered a live singleton infant at < 37 weeks gestation (n = 226; 36% Aboriginal), while controls delivered between 37 and 42 weeks gestation (n = 458; 38% Aboriginal). An interview was conducted with each subject on the postpartum unit, and information was collected from the health record. Using stratified analyses to control for race/ethnicity, several risk factors for preterm birth had a uniform effect measure across strata, while others demonstrated heterogeneity. After adjusting for other maternal characteristics in a multivariable logistic regression model, significant risk factors for all women included previous preterm birth, two or more previous spontaneous abortions, vaginal bleeding after 12 weeks gestation, gestational hypertension, antenatal hospitalisation, and prelabour rupture of membranes. In addition, potentially modifiable risk factors included low weight gain during pregnancy and inadequate prenatal care for all women, and high levels of perceived stress for Aboriginal women. These modifiable risk factors lend themselves to public health interventions, and should be targeted in future prevention efforts.     

Characteristics of preterm delivery and low birthweight among 113,994 infants in Alberta: 1994-1996

This study examined the impact of infant and maternal factors on preterm delivery and low birthweight (LBW) in Alberta between January 1, 1994 and December 31, 1996. Data on 113,994 births were collected from vital statistics registration birth data. Logistic regression models for preterm and LBW delivery suggested the key risk factors were multiple and still birth (odds ratios > 22.0). Other characteristics included female gender, birth defects, nulliparous women, maternal age 35 and greater, unmarried, history of abortion, maternal smoking, maternal street drug use, and having less than 4 prenatal visits (odds ratios 0.86-2.54). Interactions between smoking and alcohol, and smoking and parity were noted. Efforts to improve the currently low rates (8.2%) of smoking cessation during pregnancy are required. Social, economic and medical factors associated with delayed childbearing and birth outcomes should be investigated.     

Safety of MenACWY-CRM vaccine exposure during pregnancy

BackgroundAlthough the meningococcal conjugate MenACWY-CRM vaccine is not approved for use in pregnant women, unintentional exposure during pregnancy can occur, especially during early pregnancy among women of child-bearing age. This study provides safety information about inadvertent MenACWY-CRM vaccination during pregnancy.MethodsThe evaluated population consisted of pregnant female members of Kaiser Permanente Southern California who inadvertently received MenACWY-CRM at 11–21 years of age during 09/30/2011-06/30/2013 within 28 days prior to conception or during pregnancy. Chart abstraction was conducted to identify pregnancy and birth outcomes, including spontaneous and induced abortions, preterm births, low weight births, and major congenital malformations (MCMs).ResultsThere were 92 women who received MenACWY-CRM during the pregnancy exposure period, mainly during the first trimester (76.1%). Hispanics represented the largest race/ethnicity category (68.5%). Among the known pregnancy outcomes (n = 66; excluding induced abortions and unknown pregnancy outcomes), the prevalence of spontaneous abortions was 18.2% (n = 12). Among live born infants (n = 55; from 54 pregnancies), 14.5% (n = 8) were born preterm (<37 weeks gestation) and 9.1% (n = 5) had a low birthweight (<2500 g). The prevalence rate of MCMs among live born infants (n = 55) was 1.8% (n = 1).ConclusionsThis study provides baseline prevalence estimates of spontaneous abortions, preterm births, low weight births, and MCMs among women inadvertently exposed to MenACWY-CRM during the pregnancy period. These estimates appear to be comparable with U.S. background prevalence estimates.     

农村育龄妇女自然流产危险因素流行病学研究

目的:探讨安徽省农村育龄妇女自然流产的危险因素。方法:采用随机整群抽样调查、单因素分析和Logistic回归分析。结果:安徽省农村育龄妇女1962~2001年间自然流产率达4.85%,明显高于全国平均水平3.60%。单因素分析显示,体重指数过高或过低、产前无检查、孕周检查过迟、多胎次、避孕失败、孕前吸烟或吃药、孕期吸烟或吃药均增加自然流产的危险性。Logistic回归分析得出高胎次(第2胎起)、服药避孕失败而怀孕、孕期吸烟、怀孕前近期吃药均增加自然流产的危险性。结论:该省农村妊娠妇女中并不存在特别的自然流产职业性危险因素,但进一步抓好计划生育、杜绝多胎生育、加强孕期保健等对降低自然流产率和促进妇女生殖健康是有利的。     

Child-bearing after induced abortion: reassessment of risk.

We reviewed 1791 singleton pregnancies of women with a history of previous induced abortion and compared them with 14,857 pregnancies in mothers with no previous induced abortions. Therapeutic termination of pregnancy was associated with a statistically significant increase in the incidence of low birth weight infants and bleeding in the first trimester of pregnancy. When other variables were examined, no significant differences were found between the two groups, except for a significantly higher rate of stillbirths among women who had not had a prior induced abortion. There were no increases in major or minor congenital malformations.     

Influence of smoking during pregnancy on children's health--overview of epidemiologic studies

The association between maternal smoking and retarded maternal condition and birth outcome is well know. Smoking during pregnancy increases risk of spontaneous abortion, placenta previa, abruptio placenta, preterm premature rupture of membranes, stillbirth, preterm delivery and sudden infant death syndrome. The recently conducted studies also indicate that prenatal exposure to tobacco smoke is a risk factor for respiratory infections, asthma, allergy, childhood cancer, and it has neurobehavioral consequences regarding children's health. The risk for most of these conditions has been found to increase with the number of cigarettes smoked. On the other hand women who stopped smoking during pregnancy are at lower risk for most of those pathologies.     

Colonization with genital mycoplasmas in women

Factors relating to colonization by Mycoplasma hominis and T-mycoplasms were studied in 757 women. Urethral and vaginal cultures were obtained from each participant. Mycoplasmal colonization was more prevelent among black women studied at Boston City Hospital (compared with private office) and among women using oral contraceptives. Colonization with M. Hominis was also associated with examination early in the menstrual cycle. Colonization with both organisms was more prevalent among women who had gonorrhea. There was no association between mycoplasmal colonization and age, parity pregnancy, prior abortion, stillbirth, low birth weight infant, age at conception of first pregnancy, abnormal vaginal bleeding, vaginal discharge, pruritus, history of syphilis, pelvic inflamatory disease, and number of years of formal education.     

Adverse outcomes of planned and unplanned pregnancies among users of natural family planning: a prospective study.

OBJECTIVES: The purpose of this study was to determine prospectively whether unplanned pregnancies are associated with adverse pregnancy outcomes among users of natural family planning. METHODS: Women who became pregnant while using natural family planning were identified in five centers worldwide: there were 373 unplanned and 367 planned pregnancies in this cohort. The subjects were followed up at 16 and 32 weeks' gestation and after delivery. The risks of spontaneous abortion, low birth-weight, and preterm birth were estimated after adjustment by logistic regression. RESULTS: The women with unplanned pregnancies were more likely to be at the extremes of age, to report more medical problems before and during the index pregnancy, and to seek antenatal care later in gestation than the women with planned pregnancies. However, women with planned pregnancies reported a higher rate of spontaneous abortion in previous pregnancies (28.8%) than did women with unplanned pregnancies (12.9%). There were no significant differences in the rates of spontaneous abortion, low birthweight, or preterm birth between the two groups. CONCLUSIONS: No increased risk of adverse pregnancy outcomes was observed among women who experienced an unplanned pregnancy while using natural family planning.     

An epidemiological study of work with video screens and pregnancy outcome: II. A case-control study

A case-control study on work with video screen equipment during pregnancy has been made for three cohorts of women, identified with the aid of occupational codes in the census, linked to the Medical Birth Registry and a registry containing information on women hospitalized for spontaneous abortion. Five hundred and twenty-two cases were selected (women with spontaneous abortions or women who had infants that died, had severe malformations, or had a birth-weight below 1,500 g) and 1,032 controls (women who had infants without any of these characteristics) taken from the same age stratum as the cases. All pregnancies had occurred in 1980-81. Questionnaires were mailed to the women asking for information on their work situation, including questions about work with video screen equipment. Fifty-eight women were excluded for various reasons. Response rate was 93%--lower (89%) among women with spontaneous abortions than among women who gave birth (95%). As stress and smoking were associated with video screen work, the effect of video screen work was analyzed after stratification for stress and smoking--no statistically significant effect of video screen work was seen but odds ratios were above 1. Crude odds ratios for video screen work were significantly elevated and showed a dose-dependent effect. This finding is discussed from the point of view of biases in the study: selective non-responding, recall bias, geographical variability, and lack of information on women who had induced abortions. Using questionnaire data for exposure rates in the populations studied, an estimate of the effect greater than or equal to 10 hr weekly work with video screens on spontaneous abortion rate was made. The point estimate was 1.04 with a 95% confidence interval of 0.9-1.2. Analysis of 44 infants with birth defects whose mothers had worked more than 10 hr/week with video screen equipment compared to 30 infants with birth defects whose mothers had not used such equipment in early pregnancy showed no signs of specificity in the type of birth defect.     

The effect of vaginal bleeding during pregnancy on preterm and small-for-gestational-age births: US National Maternal and Infant Health Survey, 1988

We examined the effects of vaginal bleeding during pregnancy on preterm and small-for-gestational-age (SGA) births using data from the 1988 US National Maternal and Infant Health Survey. We examined the severity of vaginal bleeding and separated the preterm births into subsets by the degree of prematurity (< 32, 32-33, 34-36 weeks' gestation). We also evaluated associations stratified by race. Multiple logistic regression analysis showed that vaginal bleeding was associated with an increased risk of preterm birth, with a more pronounced elevated risk for preterm birth before 34 weeks' gestation and a notably stronger association for more severe bleeding that occurred in both the first and the second half of pregnancy. Odds ratios, but not risk differences, for birth before 34 weeks' gestation were greater for white women with vaginal bleeding than for black women. There was no association between vaginal bleeding during pregnancy and SGA births.     

Risks of delivery during the 20th to the 36th week of gestation

Using routinely collected maternity discharge data from 250,000 women in Scotland, we examined the risks of late spontaneous abortion and preterm delivery during the period 20 up to 36 weeks of gestation. Gestational age is treated as a fetal survival time and the risks of delivery associated with a history of spontaneous abortion, induced abortion and perinatal death are examined in a survival model controlling for several demographic and socioeconomic variables. The main objective of the study is to identify factors which are associated with high relative hazard of delivery early in the period, but with decreasing relative hazard of delivery as pregnancy progresses. The factor most clearly associated with converging hazards is a history of two or more spontaneous abortions, and this may reflect the tendency to repeat pregnancy outcome.     

Paternal and Maternal Smoking Habits before Conception and During the First Trimester: Relation to Spontaneous Abortion

PURPOSE: This study examined the association between maternal smoking before and during the first trimester of pregnancy and spontaneous abortion.

METHODS: We have been conducting a hospital-based case-control study on risk factors for spontaneous abortion in the greater Milan area. We collected information from 782 cases of spontaneous abortions and 1543 controls (women who delivered at term healthy infants).

RESULTS: With respect to never smokers, the odds ratio (OR) were 0.7 (95%, confidence interval (CI), 0.5–1.0) for women who quit smoking and 1.3 (95% CI, 1.0–1.6) for those who continued during pregnancy. Women who smoked more than 10 cigarettes/day in the first trimester were at increased risk of miscarriage, with an OR of 1.4 (95% CI, 1.0–2.1). No relationship was evident between the number of cigarettes smoked before conception and the risk of abortion. Likewise, no association emerged between paternal smoking and miscarriage. Moreover, no significant interaction or modification effect was obtained when strata of age and other major characteristics were investigated.

CONCLUSIONS: The risk of abortion associated with cigarette smoking during the first trimester of pregnancy was measurable and noticeable in this population, and accounted for 9% (95% CI, 6–13%) of all cases. The increased risk of spontaneous abortion in women smoking during pregnancy is a further reason to encourage pregnant women to quit.     

Underreporting of induced and spontaneous abortion in the United States: an analysis of the 2002 National Survey of Family Growth

Underreporting of induced abortions in surveys is widespread, both in countries where the procedure is illegal or highly restricted and in those where it is legal. In this study, we find that fewer than one half of induced abortions performed in the United States in 1997-2001 (47 percent) were reported by women during face-to-face interviews in the 2002 National Survey of Family Growth (NSFG). Hispanic and black women and those with low income were among the least likely to report their experience of abortion. Women were also less likely to report abortions that occurred when they were in their 20s. Second-trimester abortions were more likely to be reported than first-trimester terminations. The levels of recent spontaneous abortion reported in the 2002 NSFG were consistent with the accumulated body of clinical research, although substantially more lifetime pregnancy losses were reported on self-administered surveys than in face-to-face interviews. Subsequent research should explore strategies to improve information collected on abortion, and, in the interim, research involving pregnancy outcomes should be adjusted for unreported induced abortions.     

The effects of maternal smoking, physical stature, and educational attainment on the incidence of low birth weight

Data from the 1980 National Natality Survey were used to investigate the effects of maternal smoking, height, weight, and educational attainment on the incidence of low birth weight among white non-Hispanic married mothers aged 20-34 years, live birth order 1-3. Using multiple logistic regression to control for the effects of infant's sex, live birth order, and maternal age, women with less than 12 years education have a low birth weight odds ratio of 2.38 and women with 12 years have a low birth weight odds ratio of 1.24 relative to women with 13 or more years. After further controlling for height, weight, and smoking, these odds ratios are reduced to 1.59 and 1.11, respectively. The majority of the reduction can be attributed to differences in smoking among the education groups. Women with low education are more likely to have smoked prior to pregnancy, more likely to smoke heavily, and less likely to stop smoking during pregnancy. The odds of low birth weight increases by 26% for every five additional cigarettes smoked per day. If all women in the study population stopped smoking during pregnancy, the incidence of low birth weight would be expected to decline by 35% for those with less than 12 years education, by 20% for those with 12 years, and by 11% for those with more than 12 years. The effects of the independent variables were also estimated for two components of low birth weight: below 2,000 grams and 2,000-2,499 grams. Although the nonresponse rate for the National Natality Survey was 20%, a comparison of mail and telephone respondents suggests that the impact of nonresponse on the estimates of the logistic coefficients is minimal.