Maternal active and passive smoking and fetal growth: A prospective study in Nagoya, Japan

In order to examine the effect of maternal active and passive smoking on fetal growth, we carried out a population-based cohort study. A self-administered questionnaire was distributed to 15,207 women who notified their pregnancy from April, 1989 to March, 1991. A total of 7,411 mother-singleton infant pairs were analyzed in this study. Paternal smoking status and maternal hours exposed to environmental tobacco smoke (ETS) were used as indicators of passive smoking. Infants born to active smoking mothers were 96 g lighter, on an average, at birth than those born to non-smokers, and the relative risk for intrauterine growth retardation was 1.79 (95% confidence interval (CI) = 1.05-3.04) among active smoking mothers. Infants with smoking fathers weighted 11 g lighter, on an average, than those with non-smoking fathers, and mean birth weight of infants was reduced by 19 g among mothers exposed to ETS. The relative risk for intrauterine growth retardation in non-smoking pregnants with a smoking husband and those exposed to ETS was 0.95 (95% CI = 0.72-1.26) and 0.95 (95% CI = 0.71-1.26), respectively. Our findings indicated an adverse effect of maternal active smoking on fetal growth in Japanese pregnant population, but with small influence of maternal passive smoking.     

孕期被动吸烟对妊娠并发症及妊娠结局的影响

目的了解孕期被动吸烟发生情况,并探讨其对妊娠并发症及结局的影响。方法选取2012年4月―2013年3月在我国15家医疗保健机构分娩的8926例单胎活产产妇作为研究对象,使用自制调查问卷收集孕期被动吸烟发生情况、妊娠并发症和结局等信息,采用单因素和多因素Logistic回归分析模型分析孕期被动吸烟对妊娠并发症及结局的影响。结果共1801例产妇在孕期经历被动吸烟。控制混杂因素后,孕期经历被动吸烟的产妇妊娠期糖尿病(gestational diabetes mellitus,GDM)的发生风险是非被动吸烟者的1.359倍(95%CI:1.146~1.612,P<0.001),胎膜早破的风险为1.290倍(95%CI:1.095~1.520,P=0.002),早产的风险为1.367倍(95%CI:1.155~1.619,P<0.001),娩出低出生体重儿的风险为1.341倍(95%CI:1.079~1.668,P=0.008)。与非被动吸烟者相比,平均每周被动吸烟天数≥4天者胎膜早破、早产和低出生体重儿的发生风险分别为非被动吸烟者的1.402倍(95%CI:1.104~1.780,P=0.006)、1.690倍(95%CI:1.339~2.132,P<0.001)和1.584倍(95%CI:1.172~2.141,P=0.023)。结论被调查产妇孕期被动吸烟率较高,孕期经历被动吸烟能够增加妊娠期糖尿病、胎膜早破、早产和低出生体重儿的发生风险。     

Passive smoking by pregnant women and fetal growth.

STUDY OBJECTIVE--The aim was to investigate the effect of passive smoke exposure during pregnancy on fetal growth in the Japanese population. DESIGN--The study comprised a community based interview and clinical survey of pregnant women in Aichi Prefecture, Japan. SETTING--Participants attended for delivery at 146 private and public practices and hospital clinics in the Prefecture. SUBJECTS--Participants were 6831 women who delivered a live singleton without malformation during the three consecutive months from June 1987, and comprised about 34% of total deliveries in the Prefecture during the period. MEASUREMENTS AND MAIN RESULTS--35% of the women had been exposed passively to cigarette smoke for 2 h or more per day at home, in the work place, or in other places during pregnancy. At this level of passive exposure among non-smoking women with term deliveries (greater than or equal to 37 weeks), a small effect on fetal growth was observed; mean birth weight was reduced by 10.8 g, and the relative risk of growth retardation (less than 2500 g birth weight) was 1.0 (95% CI: 0.7-1.5), after adjusting age, parity, height, alcohol drinking, occupation, and gestation. CONCLUSIONS--The results suggest that the reduction of fetal growth associated with passive smoke exposure during pregnancy may be small in Japanese population.     

Tobacco smoke exposure and pregnancy outcome among working women. A prospective study at prenatal care centers in Orebro County, Sweden

Among 4,687 women undergoing prenatal care in Orebro County, Sweden, from October 1980 to June 1983, 678 nonsmokers reported passive exposure to tobacco smoke. Of these women, 267 had been passively exposed at work, and the risk ratio (RR) for intrauterine death (spontaneous abortion or stillbirth) among these pregnancies was increased to 1.53 (95% confidence interval (CI) 0.98-2.38) compared with pregnancies of unexposed working women. This could not be explained by age, previous spontaneous abortion, educational level, planning of pregnancy, or alcohol use. The effect was confined to first-trimester fetal loss (adjusted RR = 2.16, 95% CI 1.23-3.81), while active smoking was associated with intrauterine death after the first trimester. Passive exposure in the workplace was weakly associated with preterm birth (less than 37 weeks) but not with low birth weight (less than 2,500 g) among full-term livebirths. Active smoking clearly increased the risk of both of these outcomes. However, passive exposure in the home only did not seem to affect pregnancy outcome. The lack of quantitative exposure data points to the need for more research before passive exposure to tobacco smoke can be regarded as an established hazard to fetal development and survival.     

Cocaine use during pregnancy: perinatal outcomes

The relation between maternal cocaine use and perinatal outcomes was investigated among 17,466 non-Asian singleton deliveries in 1988 from the University of Illinois Perinatal Network data base in the metropolitan Chicago area. Elevated adjusted relative risks (RR) of low birth weight (RR = 2.8, 95% confidence interval (CI) 2.2-3.7), prematurity (RR = 2.4, 95% CI 1.9-3.1), abruptio placentae (RR = 4.5, 95% CI 2.4-8.5), and perinatal death (RR = 2.1, 95% CI 1.1-4.0) were observed for "any" cocaine users (n = 408) compared with women who did not use cocaine or any other drugs or alcohol (n = 17,058). There was an increased (although unstable) risk of intrapartum placenta previa not previously reported (RR = 2.3, 95% CI 1.0-5.1). The relative risk of small-for-gestational-age births for cocaine users who did not smoke (RR = 3.4, 95% CI 1.8-6.5) was greater than that for cocaine users who did (RR = 2.1, 95% CI 1.1-4.1). Irrespective of smoking status, cocaine use during pregnancy increased the risk of small-for-gestational-age births.     

Low birth weight in pregnancies following induced abortion: no evidence for an association

Compared with women delivering a first pregnancy, those delivering a second pregnancy after aborting the first have similar rates of low (less than 2,500 g) birth weight newborns (relative risk (RR) G2A1/G1 = 0.86, 95% confidence interval (CI) = 0.49-1.51) and mean birth weight (delta = 16.3 g, p = 0.63). Abortion of the first pregnancy prevents the reduction in low birth weight and increase in mean birth weight in the second pregnancy which delivery of the first pregnancy normally bestows (RR G2P1/G2A1 = 0.48, 95% CI = 0.25-0.90; delta = 135.3 g, p less than 0.0001). Two prior induced abortions do not significantly increase risk for low birth weight (RR G3A2/G1 = 1.14, 95% CI = 0.37-3.56) or decrease mean birth weight (delta = 29.0 g), compared with women delivering their first pregnancy. The second of two deliveries has a reduced risk of low birth weight irrespective of whether both deliveries follow an aborted first pregnancy. Adjustment for confounding factors did not materially change these results. Low birth weight rates were higher after abortions performed in hospital compared with elsewhere (p = 0.03), but mean birth weight was not affected. Gestation at abortion, vacuum aspiration or dilatation and curettage, and abortion complications were unrelated to birth weight of subsequent pregnancies. Pregnancies conceived within six months of a prior abortion or delivery had lower birth weight than if the antecedent pregnancy ended more than six months previously.     

Active and passive smoking and risk of breast cancer by age 50 years among German women

Recent studies suggest that both active and passive smokers have an increased risk of breast cancer compared with women who have never been either actively or passively exposed. Data on lifetime active and passive smoking were collected in 1999-2000 from 468 predominantly premenopausal breast cancer patients diagnosed by age 50 years and 1,093 controls who had previously participated in a German case-control study conducted in 1992-1995. Compared with never active/passive smokers, former smokers and current smokers had odds ratios of 1.2 (95% confidence interval (CI): 0.8, 1.7) and 1.5 (95% CI: 1.0, 2.2), respectively, and ever active smokers had an odds ratio of 1.3 (95% CI: 0.9, 1.9). The risk increased with duration of smoking and decreased after cessation of smoking. Among never active smokers, ever passive smoking was associated with an odds ratio of 1.6 (95% CI: 1.1, 2.4). Exposure to environmental tobacco smoke during childhood or before the first pregnancy did not appear to increase breast cancer risk. At greatest risk were women who had a high level of exposure to both passive and active smoking (odds ratio = 1.8, 95% CI: 1.2, 2.7). This study strengthens the hypothesis of a causal relation between active and passive smoke exposures and breast cancer risk.     

Low Birth Weight and Prenatal Exposure to Indoor Pollution from Tobacco Smoke and Wood Fuel Smoke: A Matched Case–Control Study in Gaza Strip

Maternal exposure to environmental tobacco smoke (ETS) is a major health hazard as it contains lower doses of the toxins that smokers?? inhale. Prenatal exposure to wood fuel smoke has been linked to delivering low birth weight (LBW) infants. The study aims to assess the association between prenatal exposure to ETS and wood fuel smoke and LBW. A case?Ccontrol study in ratio 1:1 was conducted in two hospitals with obstetric services in Gaza Strip. Subjects were selected during May?CJune and July?CAugust 2007 from attenders of Mbarak Hospital and Shifa Medical Centre, respectively. 184 (41.2%), and 79 (17.7%) out of 446 participants were exposed to environmental tobacco smoke and wood fuel smoke, respectively. Adjusted maternal exposure to ETS (especially the number of cigarettes smoked, water pipe and wood fuel smoke) was associated with LBW infants. Cigarette smoke exhibits an independent dose?Cresponse risk of LBW after adjusting for confounders. Prenatal exposure to cigarette smoke indoors is related to a reduction in birth weight of infants of ?237?g (95% CI: ?415, ?58) for pregnant women exposed to 1?C20 cigarettes per day and ?391?g (95% CI: ?642, ?140) for exposure to more than 20 cigarettes per day. Exposure to wood fuel smoke exhibits a reduction of infants?? adjusted mean birth weight by ?186?g (95% CI: ?354, ?19). Prenatal exposure to passive smoking and wood fuel smoke are independently associated with LBW. Both these factors are modifiable exposures that could possibly lead to a reduction of delivering LBW infants.     

The Association Between Second Hand Smoke and Low Birth Weight and Preterm Delivery

To determine the association between maternal exposure to SHS and low birth weight and preterm delivery. This cross-sectional study was carried out in the four main governmental hospitals dealing with deliveries in the north of Jordan. A consecutive 8,490 women who delivered in these hospitals between April 2007 and September 2007 were included in the study after excluding those who reported active smoking during the current pregnancy. Pre-structured questionnaire and review of hospital records were used to collect data about maternal background, obstetric history, medical history, and data related to second hand smoke exposure. Overall, 13.8% of women gave birth to a preterm baby and 10.0% gave birth to a low birth weight baby. About 12.6% of women who were exposed to SHS delivered low birth weight babies compared to 7.7% for non exposed women. The rate of preterm delivery among the exposed group was significantly higher than that among the non-exposed group (17.2 vs. 10.6%). In the multivariate analysis, exposure to SHS during pregnancy was significantly associated with increased odds of low birth weight (OR = 1.56 (95% CI 1.31, 1.89)) and preterm delivery (OR = 1.61 (95% CI: 1.30, 1.99)). Exposure of women to SHS during pregnancy is associated with increased odds of low birth weight and preterm delivery. Health care professionals should carry out educational programs to increase awareness and understanding of pregnant women and their husbands about the harmful effects of second hand smoke on birth outcomes.     

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.     

Active and passive smoking and risk of colds in women

PURPOSE: To evaluate the association between active and passive smoking and frequency of colds in women. METHODS: Data on cigarette smoking and frequency and duration of colds were analyzed in the Women's Health Study (WHS), a randomized, double-blind, placebo-controlled trial of low-dose aspirin and vitamin E in the primary prevention of cardiovascular disease and cancer among 39,876 female health professionals. RESULTS: After adjustment for age, body-mass index, prevalence of asthma and chronic lung diseases, alcohol intake, physical activity, and multivitamin use, current heavy smokers had no appreciable increase in the frequency of colds (relative risk (RR) for >or= 3 versus no colds in the past year, 1.05; 95% confidence interval (CI), 0.80-1.39), but a significantly increased risk of prolonged colds (RR for colds of > 7 vs. 1-3 days, 2.53; 95% CI, 1.95-3.29). There was no difference in the number of days confined to home. Nonsmoking women passively exposed to cigarette smoke had a slightly increased risk of both more frequent colds (RR, 1.33; 95% CI, 1.18-1.51) and more prolonged colds during the previous year (RR, 1.12; 95% CI, 0.99-1.27). CONCLUSIONS: Women who are currently heavy smokers are at increased risk of having colds with longer duration compared with nonsmokers. Nonsmoking women passively exposed to cigarette smoking are at slightly increased risk of having more frequent and longer colds than nonsmoking women not exposed to passive smoke.     

The association between low birth weight and caffeine consumption during pregnancy

In a prospective study of 3,891 antenatal patients at Yale-New Haven Hospital between 1980 and 1982, 76.7% consumed caffeine from coffee, tea, colas, and drugs. A dose response of caffeine intake to increased risk for delivering low birth weight (less than 2,500 g) singleton newborns was observed. This relation was observed in deliveries after 36 weeks gestational age. When comparison was made with women who had no caffeine exposure, the relative risks of low birth weight after adjustment for confounding factors were 1.4 (95% confidence interval (CI) 0.7-3.0) for 1-150 mg of caffeine daily; 2.3 (95% CI 1.1-5.2) for 151-300 mg; and 4.6 (95% CI 2.0-10.5) for over 300 mg. Decreases in mean birth weight were 6, 31, and 105 g, respectively. Gestational age did not appear to be related to caffeine consumption in the crude or adjusted analysis. Maternal caffeine intake seems to exert an effect on birth weight through growth retardation in term newborns.     

Job stress and adverse outcome of pregnancy: a causal link or recall bias?

A case-base study in a population of 214,108 commercial and clerical female workers in Denmark during the period 1983-1985 investigated whether increasing job stress, defined as increasing job demands and decreasing job control, increased the risk of an adverse outcome of pregnancy. Information on the cohort, the outcome of 24,362 pregnancies, was obtained by linkage with nationwide health registers. Six case groups were selected: 1) 2,248 spontaneous abortions, 2) 209 stillbirths or deaths within the first year of life, 3) 661 infants with congenital malformations, 3) 593 preterm deliveries, 4) 587 infants with term low birth weights, 5) 988 infants with light-for-date birth weights, and 6) a random sample of 2,252 pregnancies that constituted the reference group. Information on exposure was obtained by mailed questionnaire. When dichotomized scales on data concerning job demand and control were used, there was an increased relative risk of spontaneous abortion (odds ratio = 1.28, 95% confidence interval (CI) 1.05-1.57) and term low birth weight (odds ratio = 1.46, 95% CI 1.05-2.04) for women experiencing high job stress. For the other case groups, the odds ratios were as follows: congenital malformation, 1.23 (95% CI 0.93-1.63); preterm delivery, 1.03 (95% CI 0.77-1.39); light-for-date birth weight, 1.08 (95% CI 0.83-1.40); and stillbirth/death within the first year of life, 1.42 (95% CI 0.90-2.24). No substantial response bias was found. When occupational titles were used as an exposure matrix, no increased risk was found, except for term low birth weight. Recall bias is one possible explanation. Thus, the results must be interpreted with caution.     

孕期环境暴露对早产和低出生体重影响的队列研究

目的  探讨中国孕妇孕期环境暴露和新生儿早产及低出生体重的关系。 方法  采用自行设计的孕期环境暴露调查问卷,问卷内容包括被动吸烟、通风情况、装修情况、臭水沟、垃圾站、化工厂、高温、辐射、噪声和粉尘等环境暴露因素,对中国孕产妇队列研究项目中的孕妇进行问卷调查,随访收集新生儿的出生情况。关联性分析采用Logistic回归分析模型。 结果  本研究以6 189名孕妇为研究对象,其中283名(4.57%)孕妇早产,分娩202名(3.26%)低出生体重儿,调整年龄、民族、户口、文化程度、职业、家庭年收入、孕前体重指数(body mass index,BMI)以及产次等因素后,Logistic回归分析模型分析显示,与未接触噪声的孕妇相比,孕妇孕期在工作或居家环境中暴露于噪声环境更容易发生早产(OR=1.668,95% CI：1.197~2.323);与未接触高温的孕妇相比,孕期在工作或居家环境中暴露于高温环境的孕妇更容易发生早产(OR=2.237,95% CI：1.171~4.274)。尚未发现其他环境暴露因素与早产和低出生体重的相关性。 结论  孕期暴露于噪声和高温环境是孕妇早产的危险因素。积极开展健康宣教,减少孕妇孕期在生活工作环境中的噪声和高温暴露,可能有助于降低早产的发生风险。     

妊娠晚期血红蛋白浓度与早产和低出生体重关系的研究

目的分析妊娠晚期血红蛋白(Hb)浓度与早产和低出生体重之间的关系。方法研究对象为江苏和浙江省4个县(市)在1995—2000年间分娩的102 489名妇女。按妊娠晚期Hb浓度分四组比较各组早产和低出生体重的发生率;采用logistic回归模型控制年龄、职业、文化程度、孕次、产检次数和妊高征等因素后,估计Hb与早产和低出生体重的关联程度。结果妊娠晚期贫血患病率为48.2%,以轻度和中度贫血为主。轻、中度贫血不增加早产和低出生体重的风险。当Hb为90～99 g/L时,早产和低出生体重的发生率最低;当Hb升高或降低时,早产和低出生体重的风险均呈增加趋势。Hb为70～119 g/L时,早产和低出生体重的风险变化不大,但重度贫血和高血红蛋白则显著增加早产和低出生体重的风险:Hb<70 g/L组早产和低出生体重的OR(95%CI)分别为1.8(1.0～3.3)和4.0(2.1～7.5);Hb≥130 g/L组的早产和低出生体重的OR(95%CI)为1.2(1.0～1.4)和1.5 (1.2～1.9)。结论妊娠晚期Hb水平与早产和低出生体重的风险之间均呈"U"形趋势,妊娠晚期重度贫血以及高血红蛋白均是早产和低出生体重的危险因素。     

Enigma of maternal race and infant birth weight: a population-based study of US-born Black and Caribbean-born Black women

The authors used 1985-1990 Illinois' vital records to determine the low birth weight components of infants delivered to US-born Black women, Caribbean-born Black women, and US-born White women. The moderately low birth weight rate (1,500-2,499 g) was 10% for infants with US-born Black mothers (n = 67,357) and 6% for infants with Caribbean-born mothers (n = 2,265) compared with 4% for infants with US-born White mothers (n = 34,124); the relative risk equaled 2.7 (95% confidence interval (CI): 2.5, 2.8) and 1.7 (95% CI: 1.4, 2.0), respectively. The very low birth weight rate (<1,500 g) was 2.6% for infants delivered to US-born Black women and 2.4% for infants to Caribbean-born women compared with 0.7% for infants to US-born White women; the relative risk equaled 3.6 (95% CI: 3.1, 4.1) and 3.3 (95% CI: 2.5, 4.4), respectively. Among the lowest risk mothers, the relative risk of moderately low birth weight for infants with US-born Black mothers and Caribbean-born mothers (compared with US-born White mothers) was 2.7 (95% CI: 2.1, 3.4) and 1.2 (95% CI: 0.4, 3.1), respectively; the relative risk of very low birth weight for infants with US-born Black mothers and Caribbean-born mothers was 6.7 (95% CI: 3.8, 12) and 4.2 (95% CI: 1.0, 18), respectively. The authors conclude that Caribbean-born women and US-born Black women have disparate moderate rates but equivalent very low birth weight rates.     

Delayed childbearing: no evidence for increased risk of low birth weight and preterm delivery

Prior studies of the effect of increased maternal age on reproductive outcome in primiparous women have often ignored the possible influence on this relation of more frequent histories of spontaneous abortion and infertility in older women. When these histories are taken into account, the present study of 1,382 white primiparous women who had live singleton deliveries at Yale-New Haven Hospital finds no evidence for an increased risk of low birth weight (relative risk (RR) = 1.06, 95% confidence interval (CI) = 0.38-2.94) or preterm delivery (RR = 1.07, 95% CI = 0.50-2.24) in women delivering at age 30 years or more compared with younger women. Mean birth weight (beta = -19 g, p = 0.57) and gestational age (beta = -0.16 weeks, p = 0.34) were also not significantly affected by older maternal primiparity. Women aged 35 years or more had twice the rate of preterm births compared with women under age 30, although this result was not statistically significant in this data set (RR = 2.07, 95% CI = 0.67-6.35). Other confounding variables were taken into account.     

The influence of maternal cigarette smoking, snuff use and passive smoking on pregnancy outcomes: the Birth To Ten Study

This article describes the patterns and effects of maternal snuff use, cigarette smoking and exposure to environmental tobacco smoke during pregnancy on birthweight and gestational age, in women living in Johannesburg and Soweto in 1990. A cohort of 1593 women with singleton live births provided information about their own and household members' usage of tobacco products during pregnancy. The women completed a questionnaire while attending antenatal services. Data on gestational age and birthweight were obtained from birth records. Women who smoked cigarettes or used snuff during pregnancy accounted for 6.1% and 7.5% of the study population respectively. The mean birthweight of non-tobacco users was 3148 g [95% CI 3123, 3173] and that of the smokers 2982 g [95% CI 2875, 3090], resulting in a significantly lower mean birthweight of 165 g for babies of smoking mothers (P = 0.005). In contrast, women using snuff gave birth to infants with a mean birthweight of 3118 g [95% CI 3043, 3192], which is a non-significant (P = 0.52) decrease (29.4 g) in their infants' birthweights compared with those not using tobacco. A linear regression analysis identified short gestational age, female infant, a mother without hypertension during pregnancy, coloured (mixed racial ancestry), and Asian infants compared with black infants, lower parity, less than 12 years of education and smoking cigarettes as significant predictors of low birthweight, while the use of snuff during pregnancy was not associated with low birthweight. The snuff users, however, had a significant shorter gestational age than the other two groups of women. The birthweight reduction adjusted for possible confounders was 137 g [95% CI 26.6, 247.3 (P = 0.015)] for cigarette smokers and 17.1 g [95% CI -69.5, -102.7, P = 0.69] for snuff users respectively, compared with the birthweight of non-tobacco users. Among women who did not smoke cigarettes or use snuff, exposure to environmental tobacco smoke did not result in significant effects on the birthweight of their infants. In conclusion, infants of cigarette smokers had significantly lower birthweights than those of non-tobacco users or snuff users who are exposed to nicotine during pregnancy. Passive smoking did not affect birthweight significantly in this population.     

Prenatal active or passive tobacco smoke exposure and the risk of preterm delivery or low birth weight

We examined the association of exposure to environmental tobacco smoke with birth weight and gestational age in a large, prospective study. We also compared these endpoints between infants of active maternal smokers and those of non-smoking, non-ETS exposed women. Pregnant women were interviewed by telephone during the first trimester, and pregnancy outcome was determined for 99%. Among the 4,454 singleton live births that could be linked to their birth certificate, we confirmed increased risks of low birth weight and small for gestational age with heavier maternal smoking (> 10 cigarettes/day), as well as noting an increased risk for "very preterm" birth (< 35 weeks). These associations were generally stronger among infants of older (> or = 30 years) than those of younger mothers, as well as among non-whites. High environmental tobacco smoke exposure (> or = 7 hours/day in non-smokers) was moderately associated with low birth weight (adjusted odds ratio (AOR) 1.8, 95% confidence limits (95% CL) = 0.82, 4.1), preterm birth (AOR 1.6, 95% CL = 0.87, 2.9), and most strongly with very preterm birth (AOR 2.4, 95% CL = 1.0, 5.3). These associations were generally greater among non-whites than whites. The data support earlier studies suggesting that prenatal environmental tobacco smoke exposure, in addition to maternal smoking, affects infant health.     

Birth weight and exposure to kitchen wood smoke during pregnancy in rural Guatemala.

In this study, we aimed to establish whether domestic use of wood fuel is associated with reduced birth weight, independent of key maternal, social, and economic confounding factors. We studied 1,717 women and newborn children in rural and urban communities in rural Guatemala. We identified subjects through home births reported by traditional birth attendants in six rural districts (n = 572) and all public hospital births in Quetzaltenango city during the study period (n = 1,145). All were seen within 72 hr of delivery, and data were collected on the type of household fuel used, fire type, and socioeconomic and other confounding factors. Smoking among women in the study community was negligible. Children born to mothers habitually cooking on open fires (n = 861) had the lowest mean birth weight of 2,819 g [95% confidence interval (CI), 2,790-2,848]; those using a chimney stove (n = 490) had an intermediate mean of 2,863 g (95% CI, 2,824-2,902); and those using the cleanest fuels (electricity or gas, n = 365) had the highest mean of 2,948 g (95% CI, 2,898-2,998) (p< 0.0001). The percentage of low birth weights (< 500 g) in these three groups was 19.9% (open fire), 16.8% (chimney stove), and 16.0% (electricity/gas), (trend (p = 0.08). Confounding factors were strongly associated with fuel type, but after adjustment wood users still had a birth weight 63 g lower (p = 0.05; 95% CI, 0.4-126). This is the first report of an association between biofuel use and reduced birth weight in a human population. Although there is potential for residual confounding despite adjustment, the better-documented evidence on passive smoking and a feasible mechanism through carbon monoxide exposure suggest this association may be real. Because two-thirds of households in developing countries still rely on biofuels and women of childbearing age perform most cooking tasks, the attributable risk arising from this association, if confirmed, could be substantial.