Weight gain during the first year of life in relation to maternal smoking and breast feeding in Norway

Meta-Analysis on Associations of Timing of Maternal Smoking Cessation Before and During Pregnancy With Childhood Overweight and Obesity

INTRODUCTION

There is a lack of comprehensive review on associations of maternal smoking cessation (versus nonsmokers) with childhood overweight and obesity.

AIMS AND METHODS

We conducted a systematic review and meta-analysis of existing evidence in this field. Within PubMed, EMBASE, and CENTRAL databases, we identified and screened 1147 abstracts. We reviewed full-texts and extracted related information from 10 eligible articles. We pooled odds ratios for overweight/obesity and mean differences in BMI z-scores by maternal smoking status around pregnancy.

RESULTS

Among 10 eligible studies, 71 393 children were included from ages 2 to 18 years. Compared to children of nonsmokers, the pooled unadjusted odds ratio (OR) for overweight was 1.36 (95% Confidence Interval CI: 1.14, 1.62) in children of quitters and 1.44 (1.27, 1.64) in children of continued smokers. The pooled unadjusted OR for obesity was 1.65 (1.17, 2.32) in children of quitters and 1.94 (1.38, 2.73) in children of continued smokers. The pooled unadjusted mean difference in BMI z-score was 0.51 (0.41, 0.61) in children of quitters and 0.64 (0.58, 0.70) in children of continued smokers. The pooled unadjusted OR for overweight in children of mothers quitting before pregnancy was 1.46 (1.15, 1.85), during the first trimester was 1.52 (1.27, 1.82), and during pregnancy (mixed timing, mostly first trimester) was 0.97 (0.79, 1.20).

CONCLUSION

The risk of offspring overweight and obesity was moderately higher for quitters during pregnancy compared to nonsmokers, although it might not be as high as continued smokers.

IMPLICATIONS

Maternal smoking during pregnancy is an established risk factor of childhood overweight and obesity. Based on our systematic review, intervention to help mothers quit smoking has the potential to reduce the risk of childhood overweight and obesity in offspring related to prenatal tobacco exposure. Quitting before pregnancy is ideal, but quitting in early pregnancy is still helpful for reducing risk.

Postnatal growth in children born small for gestational age with and without smoking mother

BACKGROUND

Maternal smoking impairs fetal growth; however, if postnatal growth differs between children born small for gestational age (SGA) with smoking and non-smoking mother is unknown.

METHODS

Cohort-study of term born children born appropriate for gestational age with non-smoking mother (AGA-NS, n = 30,561), SGA (birthweight <10^th percentile) with smoking mother (SGA-S, n = 171) or SGA with non-smoking mother (SGA-NS, n = 1761). Means of height and weight measurements, collected at birth, 1.5, 3, 4, and 5 years, were compared using a generalized linear mixed effect model. Relative risks of short stature (<10^th percentile) were expressed as adjusted risk ratios (aRR).

RESULTS

At birth, children born SGA-S were shorter than SGA-NS, but they did not differ in weight. At 1.5 years, SGA-S had reached the same height as SGA-NS. At 5 years, SGA-S were 1.1 cm taller and 1.2 kg heavier than SGA-NS. Compared with AGA-NS, SGA-S did not have increased risk of short stature at 1.5 or 5 years, while SGA-NS had increased risk of short stature at both ages; aRRs 3.0 (95% CI 2.6;3.4) and 2.3 (95% CI 2.0;2.7), respectively.

CONCLUSIONS

Children born SGA-S have a more rapid catch-up growth than SGA-NS. This may have consequences for metabolic and cardiovascular health in children with smoking mothers.

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.

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.

Methods

Two databases were used: maternal check-ups during pregnancy and early infancy check-ups (between April 1, 2013 and March 31, 2014 in Okinawa, Japan) were linked via IDs and provided to us after unlinkable anonymizing. For 10,433 subjects (5229 boys and 5204 girls), we calculated the change in infants' weight z-score by subtracting the z-score of their birth weight from their weight at early infancy check-ups. Smoking exposure was categorized into five groups. We used Poisson regression to examine the association of maternal smoking during pregnancy with RWG in early infancy.

Results

Overall, 1524 (14.6%) were ex-smoker and 511 (4.9%) were current smoker. Compared with the reference category of non-smokers, the adjusted risk ratio of RWG was 1.18 (95% confidence interval [CI], 1.06–1.32) for ex-smokers, 1.18 (95% CI, 0.93–1.50) for those who smoked 1–5 cigarettes per day, 1.57 (95% CI, 1.24–2.00) for those who smoked 6–10 cigarettes per day, and 2.13 (95% CI, 1.51–3.01) for those who smoked ≥11 cigarettes per day. There was a clear dose-response relationship.

Conclusion

Our study suggests that maternal smoking during pregnancy is associated in a dose-dependent manner with increased risk of RWG in early infancy.

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Maternal smoking in pregnancy is associated with Rapid Weight Gain in early infancy.

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The association of maternal smoking with rapid weight gain was dose-dependent.

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This study was based on a large population-based dataset in Japan.

Implementation of the who Multicentre Growth Reference Study in Norway

The World Health Organization (WHO) Multicentre Growth Reference Study (MRGS) European site was Oslo, Norway. Oslo has a high breastfeeding rate. Ninety-nine percent of mothers initiate breastfeeding soon after delivery, and 80% continue for at least six months. There is no evidence that socioeconomic conditions constrain growth. As in other sites, the study had two components, longitudinal and cross-sectional. Recruitment for the longitudinal component was conducted in three hospitals that account for most births in Oslo. Approximately 850 subjects were screened in one year by using a systematic allocation scheme to recruit a sample of about 300. Recruitment for the cross-sectional component was based on a systematic interval sampling scheme prepared by the National Registry. More than 4,000 subjects were screened to achieve the required sample size. One of the major challenges of the study was to achieve an acceptable participation rate; great efforts were made to motivate pregnant women via the health care system and the media.

Tobacco smoking and breastfeeding: Effect on the lactation process, breast milk composition and infant development. A critical review

Approximately 10% of women report smoking during pregnancy. The number of breastfeeding women who relapse back to smoking is even greater. Smoking may cause adverse changes to the milk's composition by not only reducing its protective properties, but also by affecting the infant's health. The pathophysiological mechanisms underlying these adverse effects are not entirely known. This article is a review of previous reports about the effects of smoking on the lactation process, breast milk composition and infant development. A systematic search for English language articles published until 2015 was made, using a MEDLINE data. The key search terms were "smoking and breastfeeding", "smoking and lactation", "smoking and milk composition", "nicotine and breast milk". Studies have shown that nicotine levels in breast milk of women who smoke are three times higher than those in the plasma levels. Breast milk volume is reduced and the duration of lactation period is shorter. Smoking causes adverse changes to the milk's composition by not only reducing its protective properties, but also affecting infants' response to breastfeeding and to breast milk.

The influence of psychosocial factors on the duration of breastfeeding

Aim: A study was undertaken to examine to what extent psychosocial factors are related to the length of breastfeeding. Methods: A cohort of Danish mothers giving birth to a single child was followed up for four months. Information on mother and baby including psychosocial variables was obtained from a self-report questionnaire. Breastfeeding status was subsequently monitored by a health visitor. Results: A total of 471 (88%) mothers participated, 98.7 % initiated breastfeeding and after four months 277 (59%) were still exclusive breastfeeding; 99 mothers, 51% of those who stopped, stopped within the first five weeks. In Cox regression analyses the duration of breastfeeding showed a positive association with mother's schooling ( p=0.002), her intention to breastfeed ( p=0.001), previous experience with breastfeeding ( p<0.001), self-efficacy with respect to breastfeeding ( p<0.001), her confidence in breastfeeding ( p=0.012) and knowledge about breastfeeding ( p=0.001). The effect of the mother's knowledge depended on the parity of the child. Among primiparous mothers high knowledge was associated with long duration of breastfeeding, but this association was not found among the multiparous. Conclusions: To help the mothers who would like to breastfeed their baby, we must improve our ability to identify mothers at risk of early cessation. Mother's schooling, her intention, self-efficacy and earlier breastfeeding experience can be used as early predictors. An intervention should aim at improving the self-efficacy and resources of these mothers, with a focus on practical knowledge. The first five weeks, when the largest proportion of the cessations occurred, require special attention.

Maternal smoking during pregnancy and growth in infancy: a covariance structure analysis

Background

Smoking during pregnancy is related to fetal constraint and accelerated postnatal growth. However, the pathways between these factors have not been clarified. Pathway analyses that link these factors can help us better understand the mechanisms involved in this association. Therefore, this study aimed to examine pathways between maternal smoking during pregnancy and growth in infancy.

Methods

Participants were singletons born between 1993 and 2006 in rural Japan. The outcome was the change in weight z-score between birth and 3 years of age. Pathways from maternal smoking and other maternal factors (such as maternal body mass index and work status) to growth in infancy via birth factors (such as birth weight and gestational age) and breastfeeding were examined using structural equation modeling.

Results

Complete data were available for 1524 children (775 boys and 749 girls). The model fit appeared adequate. Lower birth weight and non-exclusive breastfeeding mediated the association between maternal smoking during pregnancy and rapid growth in infancy. Maternal smoking was also directly linked to rapid growth in infancy (standardized direct effects 0.06, P = 0.002). Taking all pathways into account, the standardized total effect of maternal smoking on growth in infancy was 0.11.

Conclusions

Maternal smoking during pregnancy may both indirectly, through birth weight and breastfeeding status, and directly influence growth during infancy; however, there may be other pathways that have not yet been identified.

Associated factors for accelerated growth in childhood: a systematic review

Several studies have shown that accelerated growth in the postnatal period is critical for the development of chronic diseases. The term catch-up has been used for the accelerated growth of children who have suffered some sort of restriction of nutrition or oxygen supply. However, accelerated growth has been observed among children who have an appropriate birth weight for their gestational age (AGA) and with no apparent morbidity. Therefore, this systematic review was carried out on the associated factors of accelerated growth, or catch-up, using the Medline/Pubmed database. Only cohort studies written in Portuguese, English or Spanish, with children between zero and 12 years old who presented accelerated growth or catch-up as the outcome were included. Out of the 2,155 articles found, 9 were selected. There is no uniformity in the operational definition of accelerated growth, or in the concept of catch-up. According to this review, accelerated growth is associated with primiparity, maternal smoking during pregnancy, lower birth weight, and early weaning. The main limitations in the available literature are the high number of follow-up losses and the lack of control for confounding factors. The determinants of accelerated growth still need to be studied further, especially among AGA children.

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.

Effect of passive smoking on growth and infection rates of breast-fed and non-breast-fed infants

BACKGROUND

The aim of the present study was to determine the effect of passive tobacco smoking on growth and infection rate of infants, and to evaluate whether breast-feeding might be protective against harmful effects of cigarette smoke.

METHODS

A cross-sectional study on 254 6-7-month-old infants was carried out. A questionnaire was given to mothers; and infants' head circumference, bodyweight, height, and urinary cotinine levels were measured.

RESULTS

Multivariate analysis of factors influencing lower respiratory tract infections showed that smoking mothers increased the rate by 9.1-fold; breast-feeding decreased it by 3.3-fold; formula feeding at birth increased it by a factor of 15.2; another smoker at home increased it by a factor of 40.1. Multivariate analysis of factors influencing upper respiratory tract infections showed that smoking mothers increased the rate by a factor of 23; early formula feeding increased it by a factor of 62; breast-feeding decreased it by a factor of 5; smoking fathers increased it by a factor of 15. Multivariate analysis of factors influencing otitis media found that smoking mothers and fathers increased it by a factor of 9.4 and 6.15, respectively, and breast-feeding decreased it by a factor of 5.4.

CONCLUSION

Tobacco smoke exposure of infants has negative consequences on growth, otitis media, and upper and lower respiratory tract infections. Breast-feeding promoted the growth of infants who were passively exposed to tobacco smoke and protected them against infections. Smoking should not be permitted in households with infants. When this is impossible, breast-feeding should be promoted to protect the infants against the health hazards of passive smoking.

Maternal smoking very early in pregnancy is related to child overweight at age 5-7 y

BACKGROUND

Despite being associated with lower birth weight, maternal smoking in the last 2 trimesters of pregnancy has been associated with increased risk of offspring overweight in several studies. To date, only one study has examined whether smoking in the first trimester only, which is not associated with birth weight, is also associated with childhood overweight.

OBJECTIVE

This study uses prospective data to examine associations between maternal smoking in the first compared with later trimesters of pregnancy and child overweight at age 5-7 y.

DESIGN

Data from a prospective cohort of 369 Spanish children born in 1997-1998 were used. Logistic regression was used to estimate associations between maternal smoking during different time periods and odds of child overweight later in life.

RESULTS

Maternal smoking during the first trimester was more strongly associated with overweight (adjusted odds ratio: 2.65; 95% CI: 1.26, 5.54) than smoking later in pregnancy (1.88, 0.85, 4.15). Smoking limited to the first month of pregnancy was also associated with child overweight. Neither paternal smoking nor maternal smoking before or after pregnancy was associated with child overweight. Significant interactions with breastfeeding duration indicated that first-trimester smoking was associated with overweight only among children breastfed for <6 mo, suggesting prolonged breastfeeding may help to counter adverse effects of smoking in early pregnancy.

CONCLUSIONS

These data suggest maternal smoking very early in pregnancy may increase risk of later overweight in children and provide further support for promoting smoking cessation before rather than during early pregnancy. Further studies are needed to confirm these results.

Breastfeeding duration and perinatal cigarette smoking in a population-based cohort

OBJECTIVES

We examined the association between breastfeeding duration and maternal smoking before, during, and after pregnancy.

METHODS

Data from the 2000-2001 Oregon Pregnancy Risk Assessment Monitoring System were used. Early weaning was defined as not breastfeeding at 10 weeks postpartum.

RESULTS

At 10 weeks after pregnancy, 25.7% of mothers who initiated breastfeeding no longer breastfed. After controlling for confounders, quitters (mothers who quit smoking during pregnancy and maintained quit status after pregnancy) and postpartum relapsers (mothers who quit smoking during pregnancy and resumed smoking after delivery) did not have significantly higher risk for early weaning than nonsmokers. However, persistent smokers (mothers who smoked before, during, and after pregnancy) were 2.18 times more likely not to breastfeed at 10 weeks (95% confidence interval=1.52, 2.97). Women who smoked 10 or more cigarettes per day postpartum (i.e., heavy postpartum relapsers and heavy persistent smokers) were 2.3-2.4 times more likely to wean their infants before 10 weeks than were nonsmokers.

CONCLUSIONS

Maternal smoking is associated with early weaning. Stopping smoking during pregnancy and decreasing the number of cigarettes smoked postpartum may increase breastfeeding duration.

[Household smoking and stunting for children under five years]

Maternal tobacco use during pregnancy is one of the most important factors for low birth weight and length. However, postnatal exposure to environmental tobacco smoke has not been explored in children's growth studies. It is known that smoking is more prevalent in low socioeconomic groups and that stunting is also associated with socioeconomic variables. The objective of this study was to verify the effect of socioeconomic variables and environmental tobacco smoke on growth. Children under five years (n = 2,037) attending a primary health care clinic had their weight and stature measured, and a questionnaire on exposure to household passive smoking and socio-demographic characteristics was applied to parents. Prevalence of stunting (defined as a z-score lower than -2) was 4.3%. There was a negative association between stature and smoking during pregnancy, and positive associations with socioeconomic levels, family income, and parents' education. Linear hierarchical regression analysis showed that maternal and paternal smoking remains associated with low stature even after adjusting for maternal smoking during pregnancy and for socio-demographic variables.

Maternal thiocyanate and thyroid status during breast-feeding

Cyanogenic glucosides are naturally present in plant foods especially in staple foods (cassava) consumed by millions of people in tropical countries. Most traditional processing methods are effective in detoxifying such goitrogens to safe levels of consumption. Nevertheless, residual cyanide (CN) is rapidly metabolized to thiocyanate (SCN) by existing metabolic pathways. There are concerns that goitrogens may reach the nursing infants through breast feeding or cow's milk based formulas. SCN adverse effects are commonly observed in relation to cigarette smoking. Breast-feeding is effective in protecting infants from anti-thyroid effects of eventual or habitual maternal exposure to CN exposure in food (cassava) or recreation habits (cigarette smoking). SCN goitrogenic effects occur secondary to iodine deficiency in special circumstances of high consumption of incomplete detoxified cassava and insufficient protein intake. Only during inadequate protein nutrition can SCN aggravate endemic iodine-deficient disorders (IDD).

A dose-response relationship between maternal smoking during late pregnancy and adult intelligence in male offspring

An association between maternal smoking during pregnancy and cognitive and behavioural development has been observed in several studies, but potential effects of maternal smoking on offspring adult intelligence have not been investigated. The objective of the present study was to investigate a potential association between maternal smoking during pregnancy and offspring intelligence in young adulthood. Adult intelligence was assessed at the mean age of 18.7 years by a military draft board intelligence test (Borge Priens Prove) for 3044 singleton males from the Copenhagen Perinatal Cohort with information regarding maternal smoking during the third trimester coded into five categories (about 50% of the mothers were smokers). The following potential confounders were included as covariates in multivariable analyses: parental social status and education, single mother status, mother's height and age, number of pregnancies, and gestational age. In separate analyses, birthweight and length were also included as covariates. Maternal cigarette smoking during the third trimester, adjusted for the seven covariates, showed a negative association with offspring adult intelligence (P=0.0001). The mean difference between the no-smoking and the heaviest smoking category amounted to 0.41 standard deviation, corresponding to an IQ difference of 6.2 points [95% confidence interval 0.14, 0.68]. The association remained significant when further adjusted for birthweight and length (P=0.007). Both unadjusted and adjusted means suggested a dose-response relationship between maternal smoking during pregnancy and offspring adult intelligence. When subjects with missing data were excluded, essentially the same results were obtained in the reduced sample (n=1829). These results suggest that smoking during pregnancy may have long-term negative consequences on offspring adult intelligence.

As influências ambientais e a interação homem-ecossistema no planejamento e implementação da atenção à saúde materno-infantil na prática de enfermagem

Este ensaio teórico tem como objetivo ressaltar a importância a ser dada pelo enfermeiro à questão ambiental e, especificamente, à poluição ambiental, no planejamento e implementação de ações de saúde, no que se refere à reprodução e a saúde materno-infantil. São apontados alguns efeitos de poluentes sobre a fertilidade, resultados gestacionais e crescimento e desenvolvimento da criança. É questionado o conhecimento do enfermeiro sobre esses aspectos e apresentadas considerações sobre a necessidade de aprofundar a investigação para identificar fatores de risco ambientais para a reprodução e saúde do binômio mãe-filho. A aquisição desse conhecimento pode ser uma das estratégias adotadas para que a atenção ao ambiente, incluindo as inter-relações homem-ecossistema, transforme-se em subsídio real para a adoção, pelo enfermeiro, de novas práticas em saúde. Finalmente, enfatiza a necessidade de que o enfermeiro participe em equipes multidisciplinares, nas quais sejam abordadas questões de risco para a saúde decorrentes do ambiente.

Combination of low birth weight and high adult body mass index: at what age is it established and what are its determinants?

OBJECTIVE

To investigate growth trajectories and predictive factors for those with low birth weight and high adult BMI.

DESIGN

Birth cohort study.

SETTING

England, Scotland, and Wales.

PARTICIPANTS

All born 3-9 March, 1958.

MAIN OUTCOME MEASURES

People at "high risk" of adult disease were defined as having a combination of lower birth weight (in the lowest third of the distribution) and high BMI (in the highest third of the distribution at age 33).

RESULTS

284 of 3462 men and 338 of 3555 women were identified as "high risk". This group was shorter than other cohort members at age 7, on average by 1.2 cm (boys) and 1.8 cm (girls), with a deficit of about 3 cm in adult height. The "high risk" group had a similar mean weight to other subjects at age 7, but were heavier thereafter through to age 23. BMI was increased at all ages in the "high risk" group. Independent predictors include paternal BMI, maternal height and smoking in pregnancy, and social class. For each SD increase in father's BMI the odds of low birth weight/high BMI increased by about 20%. For maternal height, a 1 cm increase reduced the odds of low birth weight/high BMI by about 5%. Increased ORs for "high risk" were found for those with manual social origins (1.61 for men; 1.49 for women) and for maternal smoking in pregnancy (1.79 and 2.27 respectively).

CONCLUSIONS

Maternal short stature, low social class, and smoking during pregnancy influence the development of "high risk" for adult chronic disease. The causes of high risk therefore seem to reside in utero and even earlier, in the mother's lifetime, with adverse conditions having a detrimental affect and favourable conditions protecting against high risk.

Does maternal smoking have a negative physiological effect on breastfeeding? The epidemiological evidence

BACKGROUND

Women who smoke are less likely to breastfeed their children than nonsmokers. It is thought that nicotine has a negative effect on breastmilk supply by suppressing prolactin levels. The aim of this review was to assess the epidemiological evidence that maternal smoking has a negative physiological effect on breastfeeding.

METHODS

The following data sources were searched: The Cochrane Library, Medline, CINAHL, Current Contents, Psychinfo, Sociological Abstracts and the Lactation Resource Centre (Australian Breastfeeding Association) using the key words "smoking" and "breastfeeding" or "infant feeding." The Journal of Human Lactation and Birth were hand searched.

RESULTS

Women who smoke are less likely to intend to breastfeed, less likely to initiate breastfeeding, and likely to breastfeed for a shorter duration than nonsmokers. Several studies have found a dose-response relationship between the number of cigarettes smoked each day and breastfeeding intention, initiation, and duration that persists after adjusting for confounding factors. In some population groups a high proportion of smokers breastfeed successfully.

CONCLUSIONS

The association between maternal smoking and lack of breastfeeding is consistent across different study designs in a range of countries. Given that women who smoke are less likely to intend to breastfeed, however, it cannot be assumed that the relationship between smoking and duration of breastfeeding is a physiological one. If smoking had a consistent negative physiological effect on lactation, one would not expect to see such wide variations in breastfeeding rates among women who smoke. Therefore, it is likely that psychosocial factors are largely responsible for the lower rates of breastfeeding found in women who smoke compared with those who do not.

Maternal smoking and reduced duration of breastfeeding: a review of possible mechanisms

AIM

To systematically review the possible mechanisms by which maternal smoking affects lactation.

METHODS

Databases (Medline, CINAHL, Current Contents, Psychinfo, Sociological Abstracts and the Cochrane Library) were searched for smoking and breastfeeding or infant feeding. The Journal of Human Lactation and Birth were hand-searched, searches were also conducted at NMAA's Lactation Resource Centre and references cited were located where appropriate. Articles were divided into the various ways that smoking could affect breastfeeding and were tabulated.

RESULTS

Most studies were conducted on small samples of animals or humans; the majority were prior to 1985. Most animal studies exposed the animals to much greater levels of nicotine than those to which humans are exposed. Most studies did not examine if breastfeeding behaviour was similar in smokers and non-smokers, and did not consider that any physiological difference found could be the result of poor lactation practices, rather than the cause of poor lactation in smokers. The definition of breastfeeding infants was also problematic in many studies. The effect of smoking on oxytocin in women was only examined in one study, and no effect was found, yet a negative effect of smoking on oxytocin release is reported in the breastfeeding literature.

CONCLUSION

Although there is consistent evidence that women who smoke breastfeed their infants for a shorter duration than non-smokers, the evidence for a physiological mechanism is not strong.

Maternal smoking and the risk of early weaning: a meta-analysis

OBJECTIVES

This study reviewed evidence on the effect of maternal smoking on early weaning.

METHODS

The following databases and journals were searched: Medline, Scientific Citation Index, Pediatrics, Journal of Pediatrics, New England Journal of Medicine, and Lancet. Analysis was restricted to studies in which infants who had never been breastfed were excluded or the prevalence of breastfeeding initiation was more than 90%.

RESULTS

In smoking vs nonsmoking mothers, the random effects odds ratio for weaning before 3 months was 1.93 (95% confidence interval [CI] = 1.55, 2.40). An adjusted odds ratio of 1.50 (95% CI = 1.34, 1.68) was shown in studies that had lost-to-follow-up rates below 15% and included adequate adjustment for confounding.

CONCLUSIONS

Maternal smoking increases the risk of early weaning.

Infant feeding practices in Ottawa-Carleton: the introduction of solid foods

Infant feeding guidelines regarding the introduction of solid foods are generally not well known in Canada. The guidelines recommend that solid foods be introduced between four to six months of age, depending on the developmental readiness of the infant. In order to understand the underlying factors and patterns which contribute to the introduction of solid foods in infants, data were analyzed from three cross-sectional surveys of parents of six-month-old infants from the Ottawa-Carleton region (n = 373, 1988; n = 330, 1992; n = 338, 1996) conducted by the Ottawa-Carleton Health Department. Multivariable analysis showed that mothers who: did not breastfeed, were younger, had lower education, smoked or had partners that smoked, and lacked support after birth, were more likely to introduce solid foods before four months of age. These data support the need for nutrition education programs to increase adherence to the new Nutrition for Healthy Term Infants guidelines.

Infant feeding practices in Ottawa-Carleton: the introduction of solid foods

Infant feeding guidelines regarding the introduction of solid foods are generally not well known in Canada. The guidelines recommend that solid foods be introduced between four to six months of age, depending on the developmental readiness of the infant. In order to understand the underlying factors and patterns which contribute to the introduction of solid foods in infants, data were analyzed from three cross-sectional surveys of parents of six-month-old infants from the Ottawa-Carleton region (n = 373, 1988; n = 330, 1992; n = 338, 1996) conducted by the Ottawa-Carleton Health Department. Multivariable analysis showed that mothers who: did not breastfeed, were younger, had lower education, smoked or had partners that smoked, and lacked support after birth, were more likely to introduce solid foods before four months of age. These data support the need for nutrition education programs to increase adherence to the new Nutrition for Healthy Term Infants guidelines.

Growth from birth to early adolescence in offspring prenatally exposed to cigarettes and marijuana

Weight, height, and head circumference were examined in children from birth to early adolescence for whom prenatal exposure to marijuana and cigarettes had been ascertained. The subjects were from a low-risk, predominantly middle-class sample participating in an ongoing longitudinal study. The negative association between growth measures at birth and prenatal cigarette exposure was overcome, sooner in males than females, within the first few years, and by the age of six, the children of heavy smokers were heavier than control subjects. Pre and postnatal environmental tobacco smoke did not have a negative effect upon the growth parameters; however, the choice of bottle-feeding or shorter duration of breast-feeding by women who smoked during pregnancy appeared to play an important positive role in the catch-up observed among the infants of smokers. Prenatal exposure to marijuana was not significantly related to any growth measures at birth, although a smaller head circumference observed at all ages reached statistical significance among the early adolescents born to the heavy marijuana users.