Factors affecting birth weight in Kuwait. Part II: Pregnancy characteristics and health factors.

The aim of this was to determine the mean birth weight of Kuwaiti infants, the incidence of low birth weight and the impact of maternal age, smoking, health status, parents' consanguinity and pregnancy characteristics on infants' birth weight. The study was conducted in the major maternity hospital in Kuwait where the body weight of 1995 newborn infants was recorded shortly after birth. Data describing maternal age, duration of pregnancy, sex of the infant and maternal illness during pregnancy were recorded. Mothers were interviewed to collect data on duration between present and last pregnancy, birth order of the infant, parents' consanguinity and frequency of smoking. The results show that the mean birth weight was 3.5 Kg and the incidence of low birth weight was 3.4%. The results illustrate that young mothers were more liable to have small infants while old mothers were more liable to deliver a very heavy or low birth weight infant. The weight of the newborn infant was positively correlated with duration of pregnancy, duration between present and last pregnancy and birth order. The mean birth weight of male infants (3.51 Kg) was higher than females (3.47 Kg). Parents' consanguinity and maternal smoking had a slight effect on infants' birth weight. The results show that diabetic mothers delivered large babies. On the contrary, the incidence of low birth weight was highest (7.0%) among infants of hypertensive mothers.     

The exposure of nonsmoking and smoking mothers to environmental tobacco smoke during different gestational phases and fetal growth

We studied the impact of maternal exposure to environmental tobacco smoke (ETS) on birth weight (BW), low birth weight (LBW), and intrauterine growth retardation (IUGR) according to self-reported maternal smoking habits in a sample of 6,866 singleton births. We obtained data about parental characteristics and maternal active smoking (AS) and passive smoking at delivery via maternal questionnaires and medical records. We used three categories of smoking habits (nonsmokers and those who smoked 1-10 or >10 cigarettes per day) and defined ETS exposure as greater than or equal to 5 cigarettes per day smoked by others in the mother's presence. We used multiple regression and logistic regression procedures with adjustment for many associated covariates. We observed a significant reduction of the mean BW in infants of AS mothers. This reduction was only marginal for mothers who stopped smoking after recognizing their pregnancy. ETS exposure in 1,797 of 5,507 nonsmoking mothers reduced the mean BW of their infants by 53 g [95% confidence interval (CI), 24-82 g]. ETS exposure also significantly reduced BW in babies of AS mothers by 92 g (CI, 21-113 g) compared with BW of ETS-nonexposed AS mothers. The adjusted odds ratio (AOR) of LBW for ETS-exposed AS mothers was two times the LBW risk of ETS-nonexposed AS mothers(2.02; CI, 1.11-3.67); the AOR of ETS-exposed nonsmoking mothers was 1.51 (CI, 1.02-2.26). The AOR of IUGR for this group did not differ from unity (1.08; CI, 0.82-1.43). However, ETS exposure increased the AOR of IUGR for AS mothers from 1.64 (CI, 1.06-2.53) to 2.13 (CI, 1.70-2.67). ETS exposure reduced the BW of infants of nonsmoking mothers and contributed to additional BW reduction in infants of AS mothers. ETS exposure increased the risk of LBW but not that of IUGR in babies of nonsmoking mothers.     

Factors affecting birth weight in Kuwait. Part I, Maternal, dietary and socioeconomic factors.

The aim of this study was to determine the effect of maternal nutrition, vitamin supplementation and socioeconomic status on infants birth weight in Kuwait. The weight of 1995 newborn Kuwaiti infants was recorded shortly after delivery. Data on mothers' bodyweight just before pregnancy, height, weight gain during pregnancy and vitamin intake were recorded. Mothers were interviewed to collect data in family income, educational level and employment during pregnancy. The results show that mean birth weight in Kuwait (3.50 Kg) compares favourably with any country. The birth weight was affected by several factors. Maternal body weight, height and weight gain during pregnancy were positively correlated with birth weight. The results also show that the intake of vitamin supplement during pregnancy did not have a significant inference on birth weight. Obese mothers consuming a reducing diet delivered babies with birth weight slightly above normal. The results show that mothers from high income families had heavier babies when compared with a low income group. On the other hand, educated and employed mothers were more liable to have slightly smaller babies when compared with illiterate or unemployed mothers.     

Effect of maternal smoking and coffee consumption on the risk of having a recognized Down syndrome pregnancy

To evaluate the possible effects of maternal smoking and caffeine or coffee consumption on the occurrence of a recognized pregnancy with Down syndrome, the authors analyzed data from a case-control study of 997 liveborn infants or fetuses with Down syndrome ascertained in California from 1991 to 1993 and 1,007 liveborn controls without a birth defect. Interviews with mothers covered demographic information, pregnancy, and medical history, with detailed questions on the use of tobacco, alcohol, and caffeinated beverages. All analyses were age-adjusted. High alcohol consumption (> or =4 drinks/week) in the first month of pregnancy was associated with reduced risk for a recognized Down syndrome conceptus (odds ratio (OR) = 0.54; 95% confidence interval (CI): 0.34, 0.85). Maternal smoking during the periconceptional period was not associated with risk of recognized Down syndrome (OR = 1.04; 95% CI: 0.79, 1.37), but maternal consumption of four or more cups of coffee per day was inversely associated (OR = 0.63; 95% CI: 0.41, 0.96). In multivariate analysis, a significant interaction between coffee drinking and smoking was observed. The inverse association remained only for nonsmoking mothers who drank four or more cups of coffee per day (OR = 0.48; 95% CI: 0.28, 0.82). These results suggest that among nonsmoking mothers, high coffee consumption is more likely to reduce the viability of a Down syndrome conceptus than that of a normal conceptus.     

The effect of paternal smoking on the birthweight of newborns whose mothers did not smoke. Group Health Medical Associates.

We examined the relationship of paternal smoking habits to birthweight in a cohort of infants enrolled at birth (n = 1219). To assess validity of parental smoking reports, cord serum levels of cotinine were measured in 175 newborns. A mean birthweight deficit of 88 g was found in newborns of nonsmoking mothers whose fathers smoked more than 20 cigarettes/day. Only 2 of 138 newborns whose mothers said they were nonsmokers had cotinine levels indicating that their mothers were active smokers. Among infants of nonsmoking mothers, detectability of cotinine in cord blood was significantly correlated with the number of cigarettes smoked daily by fathers. These data suggest that fetal growth may be adversely affected when the mother is passively exposed to tobacco smoke during pregnancy.     

Features of infant exposure to tobacco smoke in a cohort study in Tasmania.

STUDY OBJECTIVES: To document changes in smoking style around infants over time and to identify factors associated with the smoking hygiene of mothers and others. DESIGN: A population based cohort study. SETTING: Population based, involving 22% of live births in Tasmania, Australia. PARTICIPANTS: From 1 May 1988 to 30 April, 1993, 6109 infants and their mothers (89% of eligible infants) participated in the hospital and home interview of the cohort study. Infants eligible for cohort entry were those assessed at birth to be at a higher risk of SIDS. MAIN RESULTS: The overall proportion of mothers who smoked during pregnancy and postnatally did not decline. Increasing trends were found for mothers and others not smoking in the same room as baby or while holding or feeding the baby, significant over the five year period. Good smoking hygiene (mother not smoking in the same room as baby) was positively associated with--first birth (OR = 1.74 (1.30, 2.33)), low birth weight (1.69 (1.27, 2.23)), being born after 1 May 1991 (1.67 (1.33, 2.11)), and private health insurance status (1.39 (1.02, 1.90)). Good smoking hygiene was negatively associated with maternal smoking during pregnancy (0.50 (0.31, 0.80)), intention to bottle feed (0.62 (0.49, 0.78)), the level of maternal postnatal smoking, increasing numbers of smokers in the household, and parents cohabiting but unmarried. A similar analysis was conducted for other household residents who smoked. CONCLUSIONS: Changes in maternal smoking prevalence have been small. The exposure of infants to tobacco smoke postnatally has decreased significantly, although a large proportion of infants are still exposed to tobacco smoke. The identification of the above parental and infant factors associated with good smoking hygiene should be useful for health education planning.     

Maternal smoking in prenatal and early postnatal life and the risk of respiratory tract infections in infancy. The Generation R study

OBJECTIVE: To assess the associations of maternal smoking during pregnancy and in the postnatal period with respiratory tract infections in young infants. METHODS: This study was embedded in the Generation R Study, a population-based prospective cohort study from fetal life onwards. All data were assessed by questionnaires. Maternal smoking was assessed in pregnancy (no, stopped when pregnancy was known, continued during pregnancy) and at 6 months postnatally. Doctor-attended respiratory tract infections were recorded at the age of 6 months. The present analyses were based on 3,418 subjects. RESULTS: Continued maternal smoking during pregnancy was not associated with respiratory tract infections in young infants. Maternal smoking in the postnatal period showed a tendency for an increased risk of lower respiratory tract infections in infants (adjusted odds ratio (aOR) 1.61 (95% confidence interval: 0.99, 2.63)). Dose-response effects for maternal smoking during pregnancy or in the postnatal period on the risk of respiratory tract infections were not observed. In infants of mothers who smoked neither during pregnancy nor in the postnatal period, environmental smoking during pregnancy and in the postnatal period together was associated with upper respiratory tract infections (aOR 1.58 (95% CI: 1.07, 2.35)). CONCLUSIONS: No effect of maternal smoking during pregnancy with respiratory tract infections was observed. Weak evidence for the association between maternal smoking in the postnatal period and lower respiratory tract infections were found. Exposure to non-maternal environmental smoking during pregnancy and in the postnatal period together increases the risk of upper respiratory tract infections in young infants.     

Estimating the Impact of Smoking Cessation During Pregnancy: The San Bernardino County Experience

We examined the relation between maternal smoking and adverse infant outcomes [low birth weight (LBW), and preterm birth (PTB)] during 2007–2008 in San Bernardino County, California—the largest county in the contiguous United States which has one of the highest rates of infant mortality in California. Using birth certificate data, we identified 1,430 mothers in 2007 and 1,355 in 2008 who smoked during pregnancy. We assessed the effect of never smoking and smoking cessation during pregnancy relative to smoking during pregnancy for the 1,843/1,798 LBW, and 3,480/3,238 PTB’s recorded for 2007/2008, respectively. To describe the effect of quitting smoking during pregnancy, we calculated the exposure impact number for smoking during pregnancy. Major findings are: (1) relative to smoking during pregnancy, significantly lower risk of LBW among never smoking mothers [OR, year: 0.56, 2007; 0.54, 2008] and for smoking cessation during pregnancy [0.57, 2007; 0.72, 2008]; (2) relative to smoking during pregnancy, significantly lower risk of PTB was found for never smoking mothers [0.68, 2007; 0.68, 2008] and for smoking cessation during pregnancy [0.69, 2007; 0.69, 2008]; (3) an exposure impact assessment indicating each LBW or PTB outcome in the county could have been prevented either by at least 35 mothers quitting smoking during pregnancy or by 25 mothers being never smokers during pre-pregnancy. Our findings identify an important burden of adverse infant outcomes due to maternal smoking in San Bernardino County that can be effectively decreased by maternal smoking cessation.     

Determinants of developmental delay in infants aged 12 months

The aim of this study was to determine which demographic, maternal, obstetric and postnatal variables were associated with achievement of developmental milestones at the age of 12 months in term infants. Mothers and babies were enrolled in the Auckland Birthweight Collaborative Study shortly after birth. All infants were full term (gestation >or= 37 weeks). Approximately half of the sample were small for gestational age (SGA = birthweight 10th percentile). A maternal interview was conducted soon after birth. Phase 2 of the study occurred 12 months later when mothers were sent a postal questionnaire requesting information about the child's health and development during the first year of life using the Denver Prescreening Developmental Questionnaire. Seven hundred and forty-four (85.4%) European mothers returned the postal questionnaire. SGA children were not at increased risk of developmental delay at 12 months of age. In a sample representative of New Zealand European children, after adjustment for the effects of potential confounders, maternal smoking during pregnancy (OR = 2.1 [95% CI 1.1, 4.0]), maternal smoking during the first year of life (OR = 1.9 [95% CI 1.0, 3.8]) and low levels of satisfaction with parenting (OR = 2.4 [95% CI 1.1, 5.2]) were associated with significantly increased risk of developmental delay. In the subgroup of SGA children, maternal smoking during pregnancy (OR = 2.9 [95% CI 1.4, 6.2]), high levels of stress associated with parenting (OR = 2.2 [95% CI 1.2, 4.0]), and low levels of satisfaction with parenting (OR = 4.3 [95% CI 1.3, 13.5]) were significantly associated with developmental delay after adjustment for the effects of potential confounders. In conclusion, maternal and postnatal factors were better predictors of developmental delay than demographic variables.     

Childbearing characteristics of U.S.- and foreign-born Hispanic mothers

This study compares maternal and infant health and sociodemographic characteristics of U.S.-born and foreign- or Puerto Rican-born Hispanic mothers and their babies, using data from the national vital statistics system and the 1980 National Natality Survey. While nearly half of all Hispanic mothers and Mexican and Puerto Rican mothers were born in the United States, less than 10 percent of Cuban and other Hispanic mothers were U.S. born. Compared with foreign- or Puerto Rican-born Hispanic mothers, U.S.-born mothers tended to be younger, to have had fewer high-order births, to be less likely to receive delayed or no prenatal care, to have higher educational attainment, and to be more likely to be unmarried. The incidence of low birth weight among infants born to Hispanic mothers, particularly Mexican and Cuban women, was relatively low. When the proportions of low birth weight were examined by nativity status, infants born to foreign- or Puerto Rican-born women were consistently less likely to be of low birth weight. In an effort to account for these findings, the mother's smoking status before and during pregnancy is examined. Compared with non-Hispanic mothers, Hispanic mothers were much less likely to have smoked before or during pregnancy. These data are examined to see if they account for the better outcome as measured by birth weight for Hispanic births, especially those to foreign- or Puerto Rican-born women.     

Differences in BMI z-Scores between Offspring of Smoking and Nonsmoking Mothers: A Longitudinal Study of German Children from Birth through 14 Years of Age

Background: Children of mothers who smoked during pregnancy have a lower birth weight but have a higher chance to become overweight during childhood.Objectives: We followed children longitudinally to assess the age when higher body mass index (BMI) z-scores became evident in the children of mothers who smoked during pregnancy, and to evaluate the trajectory of changes until adolescence.Methods: We pooled data from two German cohort studies that included repeated anthropometric measurements until 14 years of age and information on smoking during pregnancy and other risk factors for overweight. We used longitudinal quantile regression to estimate age- and sex-specific associations between maternal smoking and the 10th, 25th, 50th, 75th, and 90th quantiles of the BMI z-score distribution in study participants from birth through 14 years of age, adjusted for potential confounders. We used additive mixed models to estimate associations with mean BMI z-scores.Results: Mean and median (50th quantile) BMI z-scores at birth were smaller in the children of mothers who smoked during pregnancy compared with children of nonsmoking mothers, but BMI z-scores were significantly associated with maternal smoking beginning at the age of 4–5 years, and differences increased over time. For example, the difference in the median BMI z-score between the daughters of smokers versus nonsmokers was 0.12 (95% CI: 0.01, 0.21) at 5 years, and 0.30 (95% CI: 0.08, 0.39) at 14 years of age. For lower BMI z-score quantiles, the association with smoking was more pronounced in girls, whereas in boys the association was more pronounced for higher BMI z-score quantiles.Conclusions: A clear difference in BMI z-score (mean and median) between children of smoking and nonsmoking mothers emerged at 4–5 years of age. The shape and size of age-specific effect estimates for maternal smoking during pregnancy varied by age and sex across the BMI z-score distribution.Citation: Riedel C, Fenske N, Müller MJ, Plachta-Danielzik S, Keil T, Grabenhenrich L, von Kries R. 2014. Differences in BMI z-scores between offspring of smoking and nonsmoking mothers: a longitudinal study of German children from birth through 14 years of age. Environ Health Perspect 122:761–767; http://dx.doi.org/10.1289/ehp.1307139     

Earlier smoking habits are associated with higher serum lipids and lower milk fat and polyunsaturated fatty acid content in the first 6 months of lactation

OBJECTIVE: To investigate the relation between maternal smoking habits, plasma lipids and milk fatty acid (FA) content and composition. DESIGN: Breastfeeding mothers who gave birth to healthy, full-term infants were recruited. Mothers were interviewed on smoking habits, being defined smokers (S) when usually smoking at least five cigarettes per day before pregnancy. SETTING: Department of Pediatrics, San Paolo Hospital, Milan, Italy. SUBJECTS: In total, 92 mothers: 61 non-S (NS) and 31 S. INTERVENTIONS: Pooled hindmilk was collected at the first raise of milk (colostrum stage), 1, 3 and 6 months, and total lipid (TL) content and fatty acid (FA) composition were evaluated. Maternal dietary habits were assessed by a food-frequency questionnaire. Two subsamples (16 NS, 6 S) were investigated after delivery and at 3 months for serum lipids and FA status. At 6 months after delivery, the number of mothers still breastfeeding decreased to 30. Variables were compared using nonparametric tests. RESULTS: In smoking mothers serum levels of triglycerides, cholesterol and low-density lipoproteins were higher, while those of high-density lipoproteins were lower. TL content in breast milk was similar in the two groups just after delivery but higher in milk from NS at 1 month. TL content and FA absolute amounts of linoleic, arachidonic, alpha-linolenic and docosahexaenoic (DHA) acid in breast milk were lower in S vs NS 1 month after delivery. Also 3 months after delivery, the breast milk of smoking mothers contained less DHA than the breast milk of nonsmoking mothers. CONCLUSIONS: Maternal cigarette smoking in early pregnancy is associated with higher plasma lipid levels and lower milk TL and DHA content in the first months of lactation.     

Is low birth weight in the causal pathway of the association between maternal smoking in pregnancy and higher BMI in the offspring?

A number of cross-sectional and prospective studies suggested a priming effect of maternal smoking in pregnancy on offspring’s obesity. It has been hypothesized that this association might be explained by low birth weight and subsequent catch-up growth in the causal pathway. We therefore examined the role of birth weight in children exposed versus not exposed to cigarette smoking in utero on later body mass index (BMI). Using data of 12,383 children and adolescents (3–17 years of age) recorded in a German population-based survey (KiGGS), we assessed mean body mass index standard deviation scores (BMI-SDS) in different birth weight SDS categories, stratified for children with smoking and non-smoking mothers. We calculated spline regression models with BMI-SDS as outcome variable, cubic splines of birth weight SDS, and potential confounding factors. Children whose mothers had been smoking during pregnancy had lower birth weight SDS and higher BMI-SDS at interview compared to children of non-smoking mothers. However, we observed a linear association between birth weight SDS and BMI-SDS in crude analyses for both groups. Similarly, almost linear effects were observed in adjusted spline regression analyses, except for children with very low birth weight. The respective 95% confidence bands did not preclude a linear effect for the whole birth weight SDS distribution. Our findings suggest that low birth weight is unlikely to be the main cause for the association between intrauterine nicotine exposure and higher BMI in later life. Alternative mechanisms, such as alterations in the noradrenergic system or increased food efficiency, have to be considered.     

Birth weights of black African babies of migrant and nonmigrant mothers compared with those of babies of European mothers in Portugal

PURPOSE: The study aim is to investigate differences in birth weights between babies of foreign-born black African, Portugal-born black African, and Portugal-born white mothers. METHODS: Hospital records for Amadora and Sintra from July 2001 to June 2002 were collated and 2949 Portugal-born white, 461 Portugal-born black African, and 817 foreign-born black African live singleton babies were identified. The impact of biologic and social factors (infant sex, maternal age, parity, gestational age, and maternal smoking, education, and occupational class) and mode of delivery on birth weights was assessed by using multivariable regression models. RESULTS: African mothers were more likely to be of lower socioeconomic status than white Portuguese mothers, among whom rates of smoking were two to three times greater (21% among white Portuguese mothers). Small preterm babies comprised 1.5% of white Portuguese babies, 2.3% of babies of Portugal-born African mothers, and 3.9% of babies of foreign-born African mothers (p < 0.05 compared with white Portuguese babies). Compared with white Portuguese babies, mean birth weight of term babies, adjusted for sex, among Portugal-born African mothers was -24.6 g (95% confidence interval, -70.1-20.9), and among foreign-born African mothers, was +38.8 g (95% confidence interval, 2.9-74.8). Adjustment for parity, maternal age, and gestational age decreased the significant birth weight advantage of babies of foreign-born African mothers to +2.3 g (95% confidence interval, -31.9-36.5). Among nonsmokers, after adjusting for these factors, white Portuguese babies were heavier (40 g; p < 0.05) than babies of foreign-born African mothers, but among smokers, they were lighter (163 g; p < 0.05). CONCLUSIONS: Compared with white Portuguese babies, mean birth weight of term babies of foreign-born African mothers was greater, and that of babies of Portugal-born African mothers was intermediate. These differences were related to a combination of biologic factors and smoking.     

Maternal smoking, birthweight and gestational age in sudden infant death syndrome (SIDS) babies and their surviving siblings

To evaluate the effect of maternal smoking on intrauterine growth of babies who died of sudden infant death syndrome (SIDS), birthweights of SIDS infants and their surviving siblings were compared with birthweights of infants in sibships were all infants survived the first year of life. We studied 184 349 mothers with at least two births registered in the population-based Swedish Medical Birth Registry during 1983–91. The mother being the unit of analysis, birthweight and gestational age of her infants were the repeated measures used in a repeated measures analysis of variance. Mothers whose first two infants survived at least 1 year, smoked less than mothers of SIDS infants, 25 and 41% ( P < 5 0.01). Overall, SIDS mothers did not smoke more while pregnant with the SIDS infant than while pregnant with the surviving sibling. SIDS siblings weighted, on average, 90 g less than infants in non-affected sibships. SIDS babies were even lighter, 193 g, and had 3.8 days shorter mean gestational age, compared with same birth-order babies in non-affected sibships. After adjustment for gestational age, the birthweight difference changed only slightly for SIDS siblings, while the difference for SIDS infants was reduced from 193 to 110 g. Further adjustment for smoking reduced the birthweight difference for SIDS siblings, from 74 to 50 g, and SIDS infants, from 110 to 82 g. Intrauterine growth retardation of sibships with a SIDS baby is explained only partly by maternal smoking. The even lower birthweight of the SIDS baby, resulting from shorter gestational age, cannot be explained by smoking, suggesting pregnancy factors specific to the SIDS baby and not to its siblings.     

Essential fatty acid composition of plasma phospholipids and birth weight: a study in term neonates

BACKGROUND: Essential fatty acids (EFAs) in umbilical cord blood samples are associated with attained birth weight in premature infants and low-birth-weight neonates. OBJECTIVE: The objective was to investigate relations between the EFA composition of cord and maternal plasma phospholipids and birth weight in term neonates. DESIGN: This was a cross-sectional study in 627 singletons born at term. The plasma phospholipid EFA composition of the mothers was determined by gas-liquid chromatography at study entry (< or = 16 wk gestation), at delivery, and in cord plasma at birth. Birth weights were normalized to SD scores. RESULTS: In cord plasma, the dihomo-gamma-linolenic acid concentration was positively related to weight SD scores. Both arachidonic acid (AA) and docosahexaenoic acid (DHA) were negatively related to weight SD scores. EFA-status indicators showed similar negative associations, whereas eicosatrienoic acid concentrations were positively related to neonatal size. In maternal plasma, proportions of n-3 long-chain polyenes (LCPs) and n-6 LCPs decreased during pregnancy. Larger decreases in AA, DHA, n-3 LCP, and n-6 LCP fractions were observed in mothers of heavier babies. Higher concentrations of LCPs in maternal plasma were, however, not related to a larger infant size at birth. CONCLUSIONS: A lower biochemical EFA status in umbilical cord plasma and a larger decrease in maternal plasma LCP concentrations are associated with a higher weight-for-gestational-age at birth in term neonates. Our findings do not support a growth-stimulating effect of AA or DHA; however, they do suggest that maternal-to-fetal transfer of EFAs might be a limiting factor in determining neonatal EFA status.     

Prenatal and intrapartum events and sudden infant death syndrome

The purpose of this study was to evaluate specific pregnancy and labour and delivery events that may increase the risk of sudden infant death syndrome (SIDS). A matched case-control study was conducted in five counties in southern California, using California death certificate records. The sample consisted of 239 Caucasian, African-American, Hispanic and Asian mothers of SIDS infants and 239 mothers of control infants matched on sex, race, birth hospital and date of birth. Mothers participated in a detailed telephone interview and provided access to obstetric and paediatric records. More case than control mothers reported a family history of anaemia (OR=2.12, P < 0.001). Placental abruptions were strongly associated with SIDS (unadjusted OR=7.94, [95% CI 1.34,47.12]). There was an increased risk of SIDS death associated with maternal anaemia during pregnancy (OR=2.51, [95% CI 1.25,5.03]), while simultaneously adjusting for maternal smoking during pregnancy, maternal years of education and age, parity, infant birthweight, gestational age, medical conditions at birth, infant sleep position and post-natal smoking. Interactions of anaemia and prenatal smoking as well as anaemia and post-natal smoking were not statistically significant. There were no other statistically significant differences between case and control mothers for pregnancy conditions, labour and delivery events (e.g. caesarean sections, anaesthesia, forceps) or newborn complications (e.g. nuchal cord, meconium aspiration). Anaemia and placental abruptions were significantly associated with an increased risk of SIDS; both are circumstances in which a fetus may become hypoxic, thereby compromising the subsequent growth, development and ultimate survival of the infant.     

Is Maternal Smoking during Early Pregnancy a Risk Factor for All Low Birth Weight Infants?

Background

Low birth weight (LBW) infants do not form a homogeneous group; LBW can be caused by prematurity or poor fetal growth manifesting as small for gestational age (SGA) infants or intrauterine growth retardation. We aimed to clarify the relationship of maternal smoking with both SGA and preterm LBW infants.

Methods

The study population comprised pregnant women who registered at the Koshu City between January 1, 1995, and December 31, 2000, and their children. We performed multivariate analyses using multiple logistic regression models to clarify the relationship of maternal smoking during pregnancy with the SGA outcome and preterm birth in LBW infants.

Results

In this study period, 1,329 pregnant women responded to questionnaires, and infant data were collected from 1,100 mothers (follow-up rate: 82.8%). The number of LBW infants was 81 (7.4%). In this cohort, maternal smoking during early pregnancy was associated with LBW and the SGA outcome. Maternal smoking during early pregnancy was a risk factor for LBW with SGA outcome and for LBW with full-term birth. However, it was not a risk factor for LBW with appropriate weight for gestational age (AGA) and LBW with preterm birth.

Conclusion

These results suggested that LBW with AGA and LBW with preterm birth were associated with other risk factors that were not considered in this study, such as periodontal disease. For the prevention of LBW, not only abstinence from smoking during pregnancy but also other methods such as establishing a clinical setting should be adopted.Key words: Infant, Low Birth Weight; Pregnancy; Risk Factors; Smoking     

Maternal smoking during pregnancy and anthropometric measurements of newborns: a population-based study in southern of Brazil

This cross-sectional study aimed to investigate the prevalence of maternal smoking during pregnancy and its impact on anthropometric measurements of newborns. A standardized questionnaire was applied to all pregnant women admitted for delivery in the maternity units in Rio Grande, Rio Grande do Sul State, Brazil, in 2007. Measurements were taken of the newborns' weight, length, and head circumference. Prevalence rates were 23% for maternal smoking during pregnancy and 29% for exposure to environmental tobacco smoke. After adjusting for potential confounding factors, compared with those whose mothers never smoked, newborns whose mothers smoked throughout pregnancy showed average decreases of 223.4 g in birth weight (95%CI: 156.7;290.0), 0.94 cm in birth length (95%CI: 0.60;1.28), and 0.69 cm in head circumference (95%CI: 0.42-0.95). In conclusion, prevalence of maternal smoking during pregnancy was high in this municipality. Maternal smoking during pregnancy was inversely associated with birth weight, length, and head circumference.