Maternal smoking cessation in early pregnancy and offspring weight status at four years of age. A prospective birth cohort study

Timing of Maternal Smoking Cessation and Newborn Weight, Height, and Head Circumference

OBJECTIVE

To examine the relationship between timing of smoking cessation during pregnancy and anthropometric indices of newborns.

METHODS

Mothers and neonates enrolled in the JECS (Japan Environment and Children's Study), a nationwide birth cohort study, were examined. Patients with full-term neonates were included in the analysis, and 73,025 mother-neonate pairs with complete data were identified. The mothers were classified into six groups according to smoking status during pregnancy (nonsmokers [Q1, n=44,198]; ex-smokers who quit before pregnancy [Q2, n=16,461]; ex-smokers who quit in the first trimester [Q3, n=8,948]; ex-smokers who quit in the second trimester [Q4, n=498]; ex-smokers who quit in the third trimester [Q5, n=651]; and smokers who smoked throughout pregnancy [Q6, n=2,269)]). Data on smoking were based on questionnaires administered in the first, second, or third trimester and 1 month after delivery. The primary outcomes were birth weight, height, and head circumference.

RESULTS

Compared with nonsmokers (Q1), no adverse outcomes were observed for ex-smokers who quit before pregnancy (Q2). The mean adjusted weights of male and female neonates were 135 g and 125 g lower, respectively, in Q6 participants than in Q1 participants. Comparing Q1 and Q6 participants, height was 0.6 cm and 0.7 cm smaller for male and female neonates, respectively. Head circumference in neonates of Q6 participants was 0.3 cm and 0.3 cm smaller for male and female neonates, respectively, than that in Q1 participants. Across all three measures, smoking cessation in the first and second trimester reduced the differential in outcomes between nonsmokers and individuals who smoked throughout pregnancy.

CONCLUSION

Smoking during pregnancy is associated with reduced newborn birth weight, height, and head circumference. Earlier smoking cessation during pregnancy reduces the adverse effects of smoking on fetal growth.

Isolation, marginalisation and disempowerment - understanding how interactions with health providers can influence smoking cessation in pregnancy

Background

Maternal smoking during pregnancy can lead to serious adverse health outcomes for both women and their infants. While smoking in pregnancy has declined over time, it remains consistently higher in women with lower socioeconomic circumstances. Furthermore, fewer women in this group will successfully quit during pregnancy.

Aim

This study explores the barriers to smoking cessation experienced by socially disadvantaged pregnant women and investigates how interactions with health providers can influence their smoking cessation journey.

Methods

Women (either pregnant or birthed in the previous 10 years, who smoked or quit smoking in pregnancy) were recruited from a metropolitan public hospital antenatal clinic in South Australia and community organisations in surrounding suburbs. Seventeen women participated in qualitative semi-structured small focus groups or interviews. The focus groups and interviews were recorded, transcribed and thematically analysed.

Findings

Four interconnected themes were identified: 1) smoking embedded in women’s challenging lives and pregnancies, 2) cyclic isolation and marginalisation, 3) feeling disempowered, and 4) autonomy and self-determination. Themes 3 and 4 are characterised as being two sides of a single coin in that they coexist simultaneously and are inseparable. A key finding is a strong unanimous desire for smoking cessation in pregnancy but women felt they did not have the necessary support from health providers or confidence and self-efficacy to be successful.

Conclusion

Women would like improvements to antenatal care that increase health practitioners’ understanding of the social and contextual healthcare barriers faced by women who smoke in pregnancy. They seek improved interventions from health providers to make informed choices about smoking cessation and would like women-centred care. Women feel that with greater support, more options for cessation strategies and consistency and encouragement from health providers they could be more successful at antenatal smoking cessation. If such changes were made, then South Australian practice could align more with best practice international guidelines for addressing smoking cessation in pregnancy, and potentially improve outcomes for women and their children.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12884-022-04720-0.

Association between maternal smoking during pregnancy and offspring overweight in U.S.-born children

BACKGROUND

The criticism of the literature on smoking during pregnancy and offspring overweight was the confounding from postnatal factors. Interaction between gestational age and prenatal maternal smoking has not yet assessed.

METHODS

We used the Third National Health and Nutrition Examination Survey (1988-1994), linked with natality files of US-born singletons aged 2 to 6 years. A body mass index in the 85th percentile or higher were considered overweight, including obesity. Gestational age was dichotomized as preterm (<37 weeks, n = 240) or full-term (n = 2125). Smoking status during pregnancy was ascertained by a questionnaire-based interview during National Health and Nutrition Examination Survey.

RESULTS

The prevalence of offspring overweight and obesity combined was 17.3% (SE = 1.3%). And 24.0% (1.3%) of mothers smoked while pregnant. A significant interaction was observed between maternal smoking and gestational age. In preterm children, a higher prevalence of overweight (34.3% [6.7%]) was found among the offspring of smoking mothers compared to non-smoking mothers (15.8% [3.6%]). After adjustment for socio-demographics, prenatal and postnatal factors, in preterm born offspring, the odds ratio of being born to smoking mothers was 2.46 (95% confidence intervals: 1.13-5.37) among children with overweight/obesity compared to children with healthy weight born to non-smoking mothers. In full-term children, the OR of being born to smoking mothers was 0.72 (0.50-1.03) among offspring with overweight/obesity relative to offspring with healthy weight born to non-smoking mothers.

CONCLUSIONS

Maternal smoking during pregnancy was strongly associated with offspring overweight and obesity in preterm births after control for postnatal factors. Preterm children of smoking mothers should be prioritized for obesity prevention.

Maternal smoking during pregnancy and offspring body mass index and overweight: a systematic review and meta-analysis

Abstract: The present study aimed to conduct a systematic review and meta-analysis to evaluate the evidence on the association of maternal smoking during pregnancy with offspring body composition in childhood, adolescence and adulthood. MEDLINE, Web of Science and LILACS databases were searched. Reference lists were also screened. We included original studies, conducted in humans, that assessed the association of maternal smoking during pregnancy with offspring body mass index (BMI) and overweight in childhood, adolescence and adulthood, published through May 1st, 2018. A meta-analysis was used to estimate pooled effect sizes. The systematic review included 64 studies, of which 37 evaluated the association of maternal smoking during pregnancy with overweight, 13 with BMI, and 14 evaluated both outcomes. Of these 64 studies, 95 measures of effect were extracted and included in the meta-analysis. We verified that the quality of evidence across studies regarding maternal smoking in pregnancy and overweight and BMI of offspring to be moderate and low, respectively. Most studies (44 studies) were classified as moderate risk bias. Heterogeneity among studies included was high and, in the random-effects pooled analysis, maternal smoking during pregnancy increased the odds of offspring overweight (OR: 1.43, 95%CI: 1.35; 1.52) and mean difference of BMI (β: 0.31, 95%CI: 0.23; 0.39). In conclusion, offspring of mothers who smoked during pregnancy have higher odds of overweight and mean difference of BMI, and these associations persisted into adulthood.

Reducing fetal origins of childhood obesity through maternal smoking cessation during pregnancy: an intervention study

Rapid infant weight gain predicts childhood obesity. We aimed to estimate effect size and identify critical timing for intervention-assisted smoking cessation during pregnancy to impact infant weight gain. We followed 25 mother-infant dyads in the UB Pregnancy and Smoking Cessation Study (Buffalo, NY, USA). Maternal smoking status was biochemically verified and monitored through pregnancy. Birth weight and length were extracted from birth records. Research staff measured infant weight and length at 2 weeks and monthly from 1–12 months of age. Mixed models were used to fit infant BMI-for-age z-score (ZBMI) trajectories. We found infants of quitters had lower ZBMI gain from birth to 12 months (mean ± SD, 1.13 ± 1.16) than infants of persistent smokers (2.34 ± 1.40; p=0.035), with Cohen’s d effect size being large (0.96). The infant ZBMI gain from birth to 12 months was low (<0.47) if smoking cessation was initiated between 15 and 27 weeks of pregnancy, but started to increase if quitting at 28 weeks (0.65) and accelerated with time (e.g., 3.16 if quitting at 36 weeks). We concluded maternal smoking cessation during pregnancy may reduce fetal origins of obesity through reducing infant weight gain, especially if quitting smoking by 27 weeks of pregnancy.

Tobacco Exposure and Conditional Weight-for-Length Gain by 2 Years of Age

Objective

To prospectively examine dose-response and timing effects of prenatal (PTE) and postnatal tobacco exposure on obesity risk assessed by conditional weight-for-length gain (CWFLG), by 2 years of age. CWFLG over the first 2 years of life was examined for 117 PTE and 57 nonexposed children. Repeated assessments of PTE were conducted beginning in the first trimester of pregnancy, using multiple methods. PTE or postnatal exposure status was not predictive of CWFLG. However, there was a dose-response association and an association with fetal exposure ascertained by infant meconium positive for nicotine and metabolites. PTE is related to restricted growth at birth, yet associated with accelerated CWFLG by 2 years of age, a measure that controls for birthweight differences. Results highlight the importance of examining dose-response and timing of exposure associations, along with the importance of obesity risk-reduction interventions within the first 2 years of life among PTE children.

The effect of prenatal smoking exposure on daily smoking among teenage offspring

AIMS

To study the predictive associations between maternal smoking and the impact of quitting smoking during pregnancy and offspring daily smoking at age 15-16 years.

DESIGN

The Northern Finland Birth Cohort 1986 (NFBC86) includes 99% of all births in the region and has an ongoing follow-up. Data were collected using questionnaires at 24th gestational week during pregnancy and after delivery, and at follow-up in 2001-02, when the offspring were aged 15-16 years.

SETTING

Northern Finland.

PARTICIPANTS

NFBC86 included 9432 live born children. Data regarding maternal smoking during pregnancy and offspring smoking at age 15-16 years were available for 4462 subjects (47.3% of the original sample).

MEASUREMENTS

The outcome was offspring's self-reported daily smoking. Maternal smoking during pregnancy was considered using a four-class variable: (1) no smoking, (2) mother had smoked, but had quit smoking before becoming pregnant, (3) mother quit smoking during the 1st trimester and (4) mother quit smoking after the 1st trimester or continued smoking throughout the pregnancy. Information regarding paternal smoking during pregnancy, maternal and paternal smoking and education level, family structure and dwelling at offspring's age 15-16 years were considered potential confounding variables.

FINDINGS

Continuing smoking after the 1st trimester increased the odds of daily smoking among offspring, independently of confounding factors [odds ratio (OR) = 1.8, 95% confidence interval (CI) = 1.3-2.5]. Continuing to smoke after the 1st trimester was associated with higher odds compared with quitting smoking during the 1st trimester. Also, parental smoking at offspring age 15-16 years increased the odds of offspring daily smoking, independently of prenatal smoking exposure.

CONCLUSIONS

Prenatal smoking exposure increases the risk for offspring adolescent daily smoking. Quitting smoking during the early stages of pregnancy may decrease the odds for offspring smoking.

Systematic review and meta-analysis of the association between maternal smoking in pregnancy and childhood overweight and obesity

BACKGROUND

By 2020, it is predicted that 60 million children worldwide will be overweight. Maternal smoking in pregnancy has been suggested as a contributing factor. Our objective was to systematically review studies on this, thereby expanding the evidence base for this association.

METHODS

Systematic review with meta-analysis, Prospero Registration number CRD42012002859. We searched PubMed, Embase, Global Health, Web of Science and the Grey literature. We included prevalence, cohort and cross-sectional studies involving full-term, singleton pregnancies. Published and unpublished studies through to 1 January 2015 in all languages, demonstrating an objective overweight outcome up until 18 years of age and data presented as an OR, were included. Quality assessment was undertaken using an adaption of the Newcastle-Ottawa scale. Statistical analysis was performed using Review Manager V.5.3.

FINDINGS

The meta-analysis included 39 studies of 236 687 children from Europe, Australia, North America and South America and Asia. Maternal smoking in pregnancy ranged from 5.5% to 38.7%, with the prevalence of overweight from 6.3% to 32.1% and obesity from 2.6% to 17%. Pooled adjusted ORs demonstrated an elevated odds of maternal smoking in pregnancy for childhood overweight (OR 1.37, 95% CI 1.28 to 1.46, I₂ 45%) and childhood obesity (OR 1.55, 95% CI 1.40 to 1.73, I₂ 24%).

INTERPRETATION

Our results demonstrate an association between maternal prenatal smoking and childhood overweight. This contributes to the growing evidence for the aetiology of childhood overweight, providing important information for policymakers and health professionals alike in planning cessation programmes or antismoking interventions for pregnant female smokers.

Risk Factors for Childhood Obesity in the First 1,000 Days: A Systematic Review

CONTEXT

Mounting evidence suggests that the origins of childhood obesity and related disparities can be found as early as the "first 1,000 days"-the period from conception to age 2 years. The main goal of this study is to systematically review existing evidence for modifiable childhood obesity risk factors present from conception to age 2 years.

EVIDENCE ACQUISITION

PubMed, Embase, and Web of Science were searched for studies published between January 1, 1980, and December 12, 2014, of childhood obesity risk factors present during the first 1,000 days. Prospective, original human subject, English-language research with exposure occurrence during the first 1,000 days and with the outcome of childhood overweight or obesity (BMI ≥85th percentile for age and sex) collected between age 6 months and 18 years were analyzed between December 13, 2014, and March 15, 2015.

EVIDENCE SYNTHESIS

Of 5,952 identified citations, 282 studies met inclusion criteria. Several risk factors during the first 1,000 days were consistently associated with later childhood obesity. These included higher maternal pre-pregnancy BMI, prenatal tobacco exposure, maternal excess gestational weight gain, high infant birth weight, and accelerated infant weight gain. Fewer studies also supported gestational diabetes, child care attendance, low strength of maternal-infant relationship, low SES, curtailed infant sleep, inappropriate bottle use, introduction of solid food intake before age 4 months, and infant antibiotic exposure as risk factors for childhood obesity.

CONCLUSIONS

Modifiable risk factors in the first 1,000 days can inform future research and policy priorities and intervention efforts to prevent childhood obesity.

Association Between Maternal Smoking During Pregnancy and Birth Weight: An Appropriately Adjusted Model From the Japan Environment and Children's Study

Background

There has been no large nationwide population-based study to examine the effects of maternal smoking status during pregnancy on birth weight that simultaneously controlled for clinical information, socioeconomic status, and maternal weight. Thus, this study aimed to determine the association between maternal smoking status during pregnancy and birth weight, while taking these confounding factors into consideration.

Methods

This study examined the first-year fixed dataset from a large nationwide birth cohort study that commenced in 2011. The dataset consisted of information on 9369 singleton infants born before December 31, 2011. Children were divided into 4 groups for statistical analysis: those born to mothers who did not smoke (NS), who quit smoking before pregnancy, who quit smoking during early pregnancy, and who smoked (SM). Multiple linear regression models were conducted for each sex to examine the association between maternal smoking status during early pregnancy and fetal growth. Birth weight was estimated using the least-squares method after controlling for covariates.

Results

After controlling for potential confounding factors, maternal smoking status during pregnancy was significantly associated with birth weight. There was a significant difference in birth weight between NS and SM for both male and female infants (male infants, 3096.2 g [NS] vs 2959.8 g [SM], P < 0.001; female infants, 3018.2 g [NS] vs 2893.7 g [SM], P < 0.001).

Conclusions

Using data from a large nationwide birth cohort study in Japan, we have shown that maternal smoking during pregnancy may reduce birth weight by 125–136 g.

Long chain polyunsaturated fatty acid supplementation in infancy increases length- and weight-for-age but not BMI to 6 years when controlling for effects of maternal smoking

Long chain polyunsaturated fatty acids (LCPUFA) are added to infant formula but their effect on long-term growth of children is under studied. We evaluated the effects of feeding LCPUFA-supplemented formula (n = 54) compared to control formula (n = 15) throughout infancy on growth from birth-6 years. Growth was described using separate models developed with the MIXED procedure of SAS(®) that included maternal smoking history and gender. Compared to children fed control formula, children who consumed LCPUFA supplemented formula had higher length-/stature-/and weight-for-age percentiles but not body mass index (BMI) percentile from birth to 6 years. Maternal smoking predicted lower stature (2-6 years), higher weight-for-length (birth-18 months) and BMI percentile (2-6 years) independent of LCPUFA effects. Gender interacted with the effect of LCPUFA on stature, and the relationship between smoking and BMI, with a larger effect for boys. Energy intake did not explain growth differences. A relatively small control sample is a limitation.

Effect of maternal smoking cessation before and during early pregnancy on fetal and childhood growth

Background

Maternal smoking during pregnancy is a major cause of intrauterine growth restriction and childhood obesity, but only a few studies have examined the association of smoking cessation before and during pregnancy with fetal and childhood growth. We examined this association in a prospective cohort study in Japan.

Methods

Our study included children born between 1991 and 2006 and their mothers. Using a questionnaire, maternal smoking status was recorded at pregnancy. The anthropometric data of the children were collected during a medical check-up at age 3 years. Multiple linear and logistic regression models were used for data analysis stratified by sex.

Results

In total, 2663 mothers reported their smoking status during early pregnancy, and data were collected from 2230 (83.7%) children at age 3 years. Maternal smoking during pregnancy was associated with a significant reduction in birth weight (approximately 120–150 g). Body mass index at age 3 years was significantly higher among boys born to smoking mothers than among boys born to nonsmoking mothers. Maternal smoking during pregnancy was associated with overweight at age 3 years among boys (adjusted odds ratio, 2.4; 95% CI, 1.03–5.4). However, among women who stopped smoking in early pregnancy, there was no increase in the risks of a small for gestational age birth or childhood overweight at age 3 years.

Conclusions

Children born to mothers who stopped smoking before or during early pregnancy had appropriate fetal and childhood growth.

Evaluation of the association between maternal smoking, childhood obesity, and metabolic disorders: a national toxicology program workshop review

BACKGROUND

An emerging literature suggests that environmental chemicals may play a role in the development of childhood obesity and metabolic disorders, especially when exposure occurs early in life.

OBJECTIVE

Here we assess the association between these health outcomes and exposure to maternal smoking during pregnancy as part of a broader effort to develop a research agenda to better understand the role of environmental chemicals as potential risk factors for obesity and metabolic disorders.

METHODS

PubMed was searched up to 8 March 2012 for epidemiological and experimental animal studies related to maternal smoking or nicotine exposure during pregnancy and childhood obesity or metabolic disorders at any age. A total of 101 studies-83 in humans and 18 in animals-were identified as the primary literature.

DISCUSSION

Current epidemiological data support a positive association between maternal smoking and increased risk of obesity or overweight in offspring. The data strongly suggest a causal relation, although the possibility that the association is attributable to unmeasured residual confounding cannot be completely ruled out. This conclusion is supported by findings from laboratory animals exposed to nicotine during development. The existing literature on human exposures does not support an association between maternal smoking during pregnancy and type 1 diabetes in offspring. Too few human studies have assessed outcomes related to type 2 diabetes or metabolic syndrome to reach conclusions based on patterns of findings. There may be a number of mechanistic pathways important for the development of aberrant metabolic outcomes following perinatal exposure to cigarette smoke, which remain largely unexplored.

CONCLUSIONS

From a toxicological perspective, the linkages between maternal smoking during pregnancy and childhood overweight/obesity provide proof-of-concept of how early-life exposure to an environmental toxicant can be a risk factor for childhood obesity.

Systematic review and meta-analyses of risk factors for childhood overweight identifiable during infancy

OBJECTIVE

To determine risk factors for childhood overweight that can be identified during the first year of life to facilitate early identification and targeted intervention.

DESIGN

Systematic review and meta-analysis.

SEARCH STRATEGY

Electronic database search of MEDLINE, EMBASE, PubMed and CAB Abstracts.

ELIGIBILITY CRITERIA

Prospective observational studies following up children from birth for at least 2 years.

RESULTS

Thirty prospective studies were identified. Significant and strong independent associations with childhood overweight were identified for maternal pre-pregnancy overweight, high infant birth weight and rapid weight gain during the first year of life. Meta-analysis comparing breastfed with non-breastfed infants found a 15% decrease (95% CI 0.74 to 0.99; I(2)=73.3%; n=10) in the odds of childhood overweight. For children of mothers smoking during pregnancy there was a 47% increase (95% CI 1.26 to 1.73; I(2)=47.5%; n=7) in the odds of childhood overweight. There was some evidence associating early introduction of solid foods and childhood overweight. There was conflicting evidence for duration of breastfeeding, socioeconomic status at birth, parity and maternal marital status at birth. No association with childhood overweight was found for maternal age or education at birth, maternal depression or infant ethnicity. There was inconclusive evidence for delivery type, gestational weight gain, maternal postpartum weight loss and 'fussy' infant temperament due to the limited number of studies.

CONCLUSIONS

Several risk factors for both overweight and obesity in childhood are identifiable during infancy. Future research needs to focus on whether it is clinically feasible for healthcare professionals to identify infants at greatest risk.

Maternal smoking during pregnancy predicts adult offspring cardiovascular risk factors - evidence from a community-based large birth cohort study

Background

Maternal smoking during pregnancy is associated with offspring obesity. However, little is known about whether maternal smoking in pregnancy predicts other offspring cardiovascular risk factors including waist circumference (WC), waist-hip-ratio (WHR), pulse rate (PR), systolic (SBP), and diastolic blood pressure (DBP).

Methods

We studied a sub-sample of 2038 (50% males) young adults who were born in Brisbane, Australia to investigate the prospective association of maternal smoking during pregnancy with young adult cardiovascular risk factors. We compared offspring mean BMI, WC, WHR, SBP, DBP and PR and the risk of being overweight and obese at 21 years by three mutually exclusive categories of maternal smoking status defined as never smoked, smoked before and/or after pregnancy but not in pregnancy or smoked during pregnancy and other times.

Results

Offspring of mothers who smoked during pregnancy had greater mean BMI, WC, WHR and PR and they were at greater risk of being obese at 21 years compared to offspring of those mothers who never smoked. The mean of these risk factors among those adult offspring whose mothers stopped smoking during pregnancy, but who then smoked at other times in the child's life, were similar to those mothers who never smoked. These results were independent of a range of potential confounding factors.

Conclusion

The findings of this study suggest a prospective association of maternal smoking during pregnancy and offspring obesity as well as PR in adulthood, and reinforce the need to persuade pregnant women not to smoke.

Tobacco smoke exposure before, during, and after pregnancy and risk of overweight at age 6

Maternal smoking during pregnancy has been associated with overweight and obesity in childhood and is strongly correlated with children's tobacco smoke exposure before and after pregnancy. We investigated the independent association of tobacco smoke exposure at various pre- and postnatal periods and overweight at age 6. A total of 1,954 children attending the 2001-2002 school entrance health examination in the city of Aachen, Germany, were included into this study. Height and weight were measured, BMI was calculated. Tobacco smoke exposure at various periods, other lifestyle and sociodemographic factors were ascertained by questionnaire. Multiple logistic regression models were used to assess the association between tobacco smoke exposure and overweight. Prevalence of overweight was 8.9%. Significant positive associations were found with maternal smoking before and during pregnancy and during the first and sixth year of life. When all smoking periods were included into one logistic model simultaneously, secondhand smoke exposure after birth remained positively associated with overweight at age 6 at either one of the two time periods (first year only: odds ratio (OR) (95% confidence interval (CI)): 2.94 (1.30-6.67), sixth year only: 2.57 (1.64-4.04), respectively) or at both (4.43 (2.24-8.76)). Exposure to tobacco smoke during the first years of life appears to be a key risk factor for development of childhood overweight.

Obesity in rural youth: looking beyond nutrition and physical activity

Contributors to excessive obesity in rural youth include well-documented nutrition and physical activity behaviors. However, emerging research suggests that preventing excessive weight gain and smoking during pregnancy, teen pregnancy, and child abuse also could reduce obesity in this vulnerable population. These traditional and emerging, nontraditional factors need to be addressed within the confines of current challenges faced by rural communities. An enhanced ecological model provides a framework for combining traditional and nontraditional factors into a more comprehensive approach that addresses the complexity of the issues contributing to youth obesity.

Growth in utero and body mass index at age 5 years in children of smoking and non-smoking mothers

BACKGROUND

High birth weight is associated with overweight later in life, while tobacco exposure in utero is associated with low birth weight, but with later risk of overweight.

AIMS

To examine whether body mass index (BMI) z-scores of children at age 5 are associated with measurements of mid-abdominal diameter (MAD) in utero comparing smoking and non-smoking mothers.

STUDY DESIGN

Growth in utero was recorded as MAD in mm per days of gestational age (MAD for gestational age) at 17, 25, 33 and 37 weeks of gestation in 561 infants whose mothers participated in a population-based study in Scandinavia (1986-1988).

OUTCOME MEASURES

The offspring's BMI z-score at 5 years was used as a dependent variable, and MAD for gestational age as well as birth weight divided by gestational age in days were included as explanatory variables in separate linear regression models. Maternal BMI was considered as a potential confounder.

RESULTS

At 17 and 25 weeks gestation there were no relevant differences in MAD for gestational age between smokers and non-smokers. At 33 and 37 weeks gestation, children of smoking mothers had less increase in MAD than children of non-smoking mothers. In adjusted models, MAD for gestational age in week 33 and 37 was positively associated with BMI z-score at 5 years of age among children of both smoking and non-smoking mothers.

CONCLUSIONS

In this study overweight in children exposed to tobacco smoking in utero was apparently not mediated through foetal growth retardation, followed by enhanced fat accretion after birth.

Denial of smoking-related risk among pregnant smokers

OBJECTIVE

To examine pregnant women's denial of risk, tobacco dependence and their partner's smoking status on smoking behavior during pregnancy.

DESIGN

Cross-sectional design with convenience sampling.

SETTING

Data collection was carried out in hospitals and antenatal clinics in Budapest and 12 other Hungarian cities.

POPULATION OR SAMPLE

A total of 406 adult pregnant women (mean age: 28.2 years; SD = 5.6) with a mean gestational age of 23.3 weeks ranging from 4 to 40 (SD = 8.9).

METHODS

Pregnant women were enrolled in the study by midwives and home-care attendants.

MAIN OUTCOME MEASURES

Smoking status was assessed by self-report questions. Further measures included the Fagerstrom Test of Nicotine Dependence to assess nicotine dependence, and the Wisconsin Inventory of Smoking Dependence Motives to assess the motivational background of smoking. Risk perception was assessed by Haslam and Draper's (2000) 12-item risk perception questionnaire.

RESULTS

Prevalence of occasional and daily smokers was 21.7 and 29.3%, respectively. Some 59.7% of the pregnant women have a partner who smokes. Daily smokers had a higher level of risk denial than occasional or non-smokers (Welch F = 91.607; p < 0.001). Current smokers also had a higher denial than temporary quitters (t = -3.153; p = 0.003). Denial of risk correlated significantly with nicotine dependence (r = 0.30) and the main motivational factors (r = 0.34-0.48). A multinomial logistic regression model of denial of risk concurrently predicted women's smoking status (p = 0.001), even when controlling for age, education, partner's smoking status and parity.

CONCLUSIONS

A higher level of risk denial seems to be one of the major determinants of women's smoking status during pregnancy.

Risk factors for childhood overweight: shift of the mean body mass index and shift of the upper percentiles: results from a cross-sectional study

BACKGROUND

The worldwide increasing prevalence of childhood overweight seems to be due to an increasing proportion of extremely high body mass index (BMI) values rather than to a shift of the entire BMI distribution. These findings might be attributed to incremental exposure to risk factors particularly affecting overweight children.

OBJECTIVE

To assess the possible differences in associations of several risk factors by subgroups of children's BMI distribution.

METHODS

We applied quantile regression to cross-sectional data on 9698 German preschoolers (5-6 years) collected in 1999 and 2002. Sex- and age-specific BMI standard deviation scores (BMI-SDSs) were used as the outcome variable, and maternal BMI, maternal smoking during pregnancy, exclusive formula feeding, child's weight gain from birth to 2 years of life and low parental education as explanatory variables.

RESULTS

All risk factors except formula feeding contributed to a positive shift in mean BMI-SDS. The estimated effects of all risk factors on BMI-SDS were greatest for children with the highest BMI-SDS value. For example, high television (TV) viewing (>2 h day(-1)) had an effect of 0.46 (95% confidence interval (CI): 0.46, 0.46) SDS units on overweight children (90th percentile), but only a 0.22 (95% CI: 0.11, 0.33) SDS effect on normal-weight children (50th percentile).

CONCLUSIONS

For well-known risk factors of childhood overweight, stronger associations in children with higher BMI values were observed. These findings might possibly help to explain the secular shift in the upper BMI percentiles in children.