Maternal smoking during pregnancy and childhood obesity

A recent cohort study suggested that maternal smoking during pregnancy might be a risk factor for childhood obesity. Data from the obligatory school entry health examination in six Bavarian (Germany) public health offices in 1999-2000 were used to assess the relation between maternal smoking during pregnancy and childhood obesity (n = 6,483 German children aged 5.00-6.99 years). A body mass index greater than the 90th percentile was defined as overweight, and a body mass index greater than the 97th percentile was defined as obesity. The main exposure was maternal smoking during pregnancy. The prevalences of overweight and obesity, expressed as percentages, increased in the following order: never smoked (overweight: 8.1, 95% confidence interval (CI): 7.2, 9.0; obesity: 2.2, 95% CI: 1.7, 2.7); less than 10 cigarettes daily (overweight: 14.1, 95% CI: 11.1, 17.7; obesity: 5.7, 95% CI: 3.7, 8.2); and 10 or more cigarettes daily (overweight: 17.0, 95% CI: 10.1, 26.2; obesity: 8.5, 95% CI: 3.7, 16.1). The adjusted odds ratios for maternal smoking during pregnancy were 1.43 (95% CI: 1.07, 1.90) for overweight and 2.06 (95% CI: 1.31, 3.23) for obesity. A dose-dependent association between overweight/obesity and maternal smoking during pregnancy was observed that could not be explained by a wide range of confounders, suggesting that intrauterine exposure to inhaled smoke products rather than lifestyle factors associated with maternal smoking accounts for this finding.     

Maternal smoking during pregnancy and smoking by adolescent daughters.

OBJECTIVES. Since cigarette smoking in adolescence represents a crucial entry point in the progression to illicit drugs, risk factors for adolescent smoking have public health implications. The influence of mothers on children's smoking appears to be greater than that of fathers. To explain the selective influence of mothers, we examined the consequences of maternal smoking during pregnancy in two longitudinal samples. METHODS. Analyses were conducted on follow-up interview data from two dyadic samples of mothers and firstborn adolescents for whom data on maternal smoking during and after pregnancy were available (192 mother-child pairs originating from New York State and 797 dyads from a national sample). RESULTS. In both samples, maternal smoking during pregnancy, when postnatal smoking was controlled, selectively increased the probability that female children would smoke and would persist in smoking (adjusted odds ratios of about 4). CONCLUSIONS. The findings suggest that nicotine or other substances released by maternal smoking can affect the fetus, perhaps through the nicotinic input to the dopaminergic motivational system, so as to predispose the brain in a critical period of its development to the subsequent addictive influence of nicotine consumed more than a decade later in life.     

Maternal vitamin D intake during pregnancy and early childhood wheezing

BACKGROUND: Maternal intake of vitamin D in pregnancy is a potentially modifiable but understudied risk factor for the development of asthma in children. OBJECTIVE: We investigated whether maternal vitamin D intake in pregnancy is associated with decreased risks of wheezing symptoms in young children. DESIGN: Subjects were from a birth cohort recruited in utero with the primary objective of identifying associations between maternal diet during pregnancy and asthma and allergies in children. A random sample of 2000 healthy pregnant women was recruited while attending antenatal clinics at the Aberdeen Maternity Hospital, Scotland, at approximately 12 wk gestation. Maternal vitamin D intake was ascertained from a food-frequency questionnaire completed at 32 wk of gestation. The main outcome measures were wheezing symptoms, spirometry, bronchodilator response, atopic sensitization, and exhaled nitric oxide at 5 y. RESULTS: Respiratory details through 5 y and maternal food-frequency-questionnaire data were available for 1212 children. In models adjusted for potential confounders, including the children's vitamin D intake, a comparison of the highest and lowest quintiles of maternal total vitamin D intake conferred lower risks for ever wheeze [odds ratio (OR): 0.48; 95% CI: 0.25, 0.91], wheeze in the previous year (OR: 0.35; 95% CI: 0.15, 0.83), and persistent wheeze (OR: 0.33; 95% CI: 0.11, 0.98) in 5-y-old children. In addition, lower maternal total vitamin D intakes in pregnancy were also associated with decreased bronchodilator response (P = 0.04). No associations were observed between maternal vitamin D intakes and spirometry or exhaled nitric oxide concentrations. CONCLUSION: Increasing maternal vitamin D intakes during pregnancy may decrease the risk of wheeze symptoms in early childhood.     

Maternal smoking during pregnancy and offspring IQ

BACKGROUND: Maternal smoking in pregnancy lowers birthweight. It is unclear, however, whether smoking during pregnancy lowers offspring IQ, and, if it does, whether it is through the smoking effect on fetal growth. METHOD: Representative samples of low birthweight (<2500 g) and normal birthweight children born in 1983-85 from inner-city and suburban communities in southeast Michigan, USA were assessed at ages 6, 11, and 17, using Wechsler intelligence tests. Smoking during pregnancy was ascertained from mothers at the first assessment; and smoking at any time was ascertained at the first and second assessment. Generalized estimating equation models were used, with children's IQ at all three assessments as outcomes (n = 798). RESULTS: Without adjustment, offspring of mothers who smoked during pregnancy scored 6.8 IQ points lower than offspring of mothers who never smoked, on average. Low birthweight children scored 5.4 IQ points lower than normal birthweight children, on average. The statistical association of maternal smoking with offspring IQ was confounded by maternal characteristics, chiefly, maternal cognitive ability as measured by IQ and education; adjustment for these factors eliminated the association. By contrast, adjustment for maternal IQ and education as well as smoking during pregnancy had a negligible effect on the low birthweight-related IQ deficit. Low birthweight did not mediate the association of smoking and lowered IQ in offspring. CONCLUSION: Maternal smoking during pregnancy is a proxy for a matrix of vulnerabilities for adverse child cognitive development and has no direct causal effect on child's IQ. The relationship of low birthweight and IQ is independent of maternal smoking and maternal cognitive abilities.     

Maternal smoking and childhood asthma.

The role of maternal smoking as a causal factor for the incidence of childhood asthma is still not clearly established. It was investigated among 3- and 4-year-old-child incident cases confirmed by a 6-year follow-up (n = 294) and cases who no longer had symptoms after diagnosis (n = 110). The study took place in Montréal, Canada, between 1988 and 1997. Persistent and transient cases were compared with their respective controls from the original case-control study of incidence. The odds ratio for heavy maternal smoking adjusted for known risk factors for asthma was 3.84 (95% confidence interval: 1.68, 8.76) among persistent cases and close to one among transient cases.     

Maternal smoking during pregnancy and childhood growth trajectory: a random effects regression analysis

Background

Although maternal smoking during pregnancy has been reported to have an effect on childhood overweight/obesity, the impact of maternal smoking on the trajectory of the body mass of their offspring is not very clear. Previously, we investigated this effect by using a fixed-effect model. However, this analysis was limited because it rounded and categorized the age of the children. Therefore, we used a random-effects hierarchical linear regression model in the present study.

Methods

The study population comprised children born between 1 April 1991 and 31 March 1999 in Koshu City, Japan and their mothers. Maternal smoking during early pregnancy was the exposure studied. The body mass index (BMI) z-score trajectory of children born to smoking and non-smoking mothers, by gender, was used as the outcome. We modeled BMI trajectory using a 2-level random intercept and slope regression.

Results

The participating mothers delivered 1619 babies during the study period. For male children, there was very strong evidence that the effect of age in months on the increase in BMI z-score was enhanced by maternal smoking during pregnancy (P < 0.0001). In contrast, for female children, there was only weak evidence for an interaction between age in months and maternal smoking during pregnancy (P = 0.054), which suggests that the effect of maternal smoking during pregnancy on the early-life BMI trajectory of offspring differed by gender.

Conclusions

These results may be valuable for exploring the mechanism of fetal programming and might therefore be clinically important.Key words: body mass index, childhood growth, gender, multi-level analysis, pregnancy, smoking     

Maternal smoking during pregnancy and limb reduction malformations in Sweden.

OBJECTIVE: This study was undertaken to investigate a possible connection between different types of limb reduction defects and maternal smoking during pregnancy. METHODS: With the use of the Swedish health registries, 610 cases of limb reduction malformations were selected from among 1 109 299 infants born between 1983 and 1993 with known smoking exposure in early pregnancy. Confounders such as maternal age and parity were controlled for with the use of the Mantel-Haenszel technique. RESULTS: The odds ratio for any maternal smoking among all cases of limb reductions was 1.26 (95% confidence interval = 1.06, 1.50). The main subgroups of limb reduction defects showed similar odds ratios, but in longitudinal reduction defect, only unilateral cases showed an association with maternal smoking. CONCLUSIONS: This study supports an association between maternal smoking and limb reduction malformations, but further work is needed before a causal inference can be made.     

Maternal smoking during pregnancy and rapid weight gain from birth to early infancy

Background

Although several studies have focused on the association between maternal smoking during pregnancy and rapid weight gain (RWG) during infancy, the dose-response relationship has not yet been confirmed, and very few studies have included Asian populations. Using a record-linkage method, we examined the association between maternal smoking during pregnancy and RWG in infants at around 4 months of age to clarify the dose-response relationship.

Maternal smoking in pregnancy, fetal development, and childhood asthma

OBJECTIVES: We examined the relationships among maternal smoking in pregnancy, fetal development, and the risk of asthma in childhood. METHODS: We conducted a population-based cohort study, where all 58 841 singleton births were followed for 7 years using nationwide registries. RESULTS: Maternal smoking increased the risk of asthma (adjusted odds ratio = 1.35; 95% confidence interval = 1.13, 1.62 for high exposure). Low birthweight and preterm delivery increased the risk of asthma at the age of 7, whereas being small for gestational age did not. CONCLUSIONS: Maternal smoking in pregnancy increases the risk of asthma during the first 7 years of life, and only a small fraction of the effect seems to be mediated through fetal growth.     

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.     

Maternal obesity in pregnancy and respiratory health in early childhood

Obesity is associated with systemic inflammation, immunological changes, increased risk of respiratory infections and chronic respiratory illness. Maternal obesity in pregnancy increases the risk of pregnancy complications, caesarean sections and adverse birth outcomes, which have in turn been associated with respiratory illness in children. To our knowledge, the possible influence of maternal obesity in pregnancy on respiratory illness in early childhood beyond the newborn period has not been explored. We examined the relationship between a high maternal body mass index (BMI) in pregnancy and lower respiratory tract infections and wheeze up to 18 months of age in the Norwegian Mother and Child Study (MoBa), a population-based cohort study that includes 100 000 pregnant women, conducted at the Norwegian Institute of Public Health. We analysed data from the first 33 192 children, born between 1999 and 2005.
In unadjusted analyses maternal obesity in pregnancy was related to both respiratory infections and wheeze in the children. In multivariable analyses, only an effect on wheeze remained. The risk of wheeze increased linearly with maternal BMI in pregnancy, and was 3.3% higher [95% CI 1.2, 5.3] for children with mothers who were obese during pregnancy, than for children of mothers with normal BMI. This effect was not mediated through obesity-related pregnancy complications, low birthweight, preterm birth or caesarean section.     

Maternal cigarette smoking during pregnancy and risk of oral clefts in newborns.

The results of previous epidemiologic research on the possible association between maternal smoking during pregnancy and risk of oral clefts in offspring have been inconsistent. This may be due in part to methodological limitations, including imprecise measurement of tobacco use, failure to consider etiologic heterogeneity among types of oral clefts, and confounding. This analysis, based on a large case-control study, further evaluated the effect of first trimester maternal smoking on oral facial cleft risk by examining the dose-response relationship according to specific cleft type and according to whether or not additional malformations were present. A number of factors, including dietary and supplemental folate intake and family history of clefts, were evaluated as potential confounders and effect modifiers. Data on 3,774 mothers interviewed between 1976 and 1992 by the Slone Epidemiology Unit Birth Defects Study were used. Study subjects were actively ascertained from sites in areas around Boston, Massachusetts and Philadelphia, Pennsylvania; the state of Iowa; and southeastern Ontario, Canada. Cases were infants with isolated defects--cleft lip alone (n = 334), cleft lip and palate (n = 494), or cleft palate alone (n = 244)--and infants with clefts plus (+) additional malformations: cleft lip+ (n = 58), cleft lip and palate+ (n = 140), or cleft palate+ (n = 209). Controls were infants with defects other than clefts, excluding defects possibly associated with maternal cigarette use. There were no associations with maternal smoking for any oral cleft group, except for a positive dose response among infants with cleft lip and palate+ (for light smokers, odds ratio (OR) = 1.09 (95% confidence interval (CI): 0.6, 1.9); for moderate smokers, OR = 1.84 (95% CI: 1.2, 2.9); and for heavy smokers, OR = 1.85 (95% CI: 1.0, 3.5), relative to nonsmokers). This finding may be related to the additional malformations rather than to the cleft itself.