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

https://doi.org/10.1016/j.earlhumdev.2008.05.009Get rights and content

Abstract

Background:

Maternal smoking during pregnancy is associated with fetal growth restriction, but also with increased risk for overweight in childhood. If the mother stops smoking in early pregnancy fetal growth is not restricted, but whether the risk for later overweight persists is unclear.

Aim:

To study if four year old children of mothers who stopped smoking in early pregnancy have higher mean body mass index (BMI) and/or increased odds of being overweight compared with children of non-smokers.

Study Design:

Prospective population based study on Norwegian mothers and children.

Subjects:

Among 711 children available for analysis, 540 were children of never smoking mothers, 114 of mothers who stopped smoking in early pregnancy, and 57 of mothers who continued to smoke throughout pregnancy.

Outcome Measures:

BMI and overweight defined by international criteria at age four.

Results:

Compared with children of never smoking mothers, children of smoking mothers had higher mean BMI (mean difference: 0.47; 95% CI: 0.10, 0.84 kg/m2), whereas mean BMI was not higher among children of mothers who stopped smoking (mean difference: 0.02; 95% CI: -- 0.24, 0.28 kg/m2. Similarly, children of smoking mothers had increased odds for overweight (adjusted OR: 2.83; 95% CI: 1.13, 7.10), whereas children of mothers who stopped smoking did not have increased odds (adjusted OR: 1.29; 95% CI: 0.62, 2.68) compared with children of never smoking mothers.

Conclusions:

In this study, the association between smoking exposure and childhood overweight did not persist in children of mothers who stopped smoking early in pregnancy.

Introduction

Tobacco exposure during pregnancy is a significant environmental cause of intrauterine growth retardation and low birth weight [1], [2]. It is also well documented that this restriction of fetal growth may be prevented, or reduced if the mother quits smoking early in pregnancy [3].

Recently, a number of studies have also reported that smoking exposure in utero increases the risk for childhood overweight [4], [5], [6], and this association has also been confirmed in two meta-analyses [7], [8]. In one of these meta-analysis, Oken et al. concluded that 715 000 US children may be overweight because their mothers smoke during pregnancy. However, whether the risk of later overweight and obesity persists if the pregnant mother quits smoking is uncertain. None of the two meta-analyses concluded on the effect of stopping smoking during pregnancy, suggesting that this question has not been adequately addressed so far. Four studies with conflicting results have been published. A study by Toschke et al. [9] showed that even children of mothers who stopped smoking prior to pregnancy had increased risks of overweight and obesity. In contrast, three other studies found no increased risk for later overweight if the mother stopped smoking before or in early pregnancy [10], [11], [12] However, the study by Al Mamun et al. [12] included those who had smoked either before or after pregnancy in the ex smoker group, and the study by Chen et al. [11] was only able to show a marginal association between smoking in pregnancy and overweight at age four, making it even less likely to show any effect of smoking cessation.

Overweight in childhood has been shown to track into adulthood [13], [14], and thereby to increase the risk for cardiovascular disease and premature death [15]. Thus, prevention of childhood overweight and obesity may have long term effects on the incidence of cardiovascular disease later in life.

We therefore aimed to study if children of mothers who quit smoking early pregnancy still have increased risk of becoming overweight at four years of age.

Section snippets

Study design

The present study uses data recorded in the Prevention of Allergy among Children in Trondheim study (PACT) [16] and data recorded at regular examinations at public health centers in Trondheim. Trondheim is a city in central Norway with 160 000 inhabitants and had approximately 2100 deliveries per year in the study period.

The PACT study is a large population based intervention study on the efficacy of systematic and structured intervention on reduced tobacco exposure, improved indoor climate and

Statistical methods

Bivariate associations between maternal smoking and the different possible covariates were analyzed using chi-square- or T-test statistics.

A general linear model was used to calculate adjusted mean childhood BMI in the three groups of maternal smoking status, and the adjusted mean difference in BMI between these groups. Precision of the estimated means was assessed by 95% confidence intervals (CIs). Logistic regression was used to calculate crude and adjusted odds ratios (ORs) with 95% CIs for

Results

Of the 711 mothers, 540 (76%) were never smokers, 114 (16%) were smokers who had quitted smoking early in pregnancy and 57 (8%) were smokers throughout pregnancy. Some characteristics of the study population are presented in Table 1.

The mean (SD) number of cigarettes smoked per day before pregnancy was 6 [5] among those who stopped smoking when they learned that they had become pregnant, compared to 11 [8] among those who persisted smoking. In addition, mothers who continued to smoke throughout

Discussion

In this study we found that children of mothers who stopped smoking did not have higher BMI, nor did this group have increased odds for overweight compared with children of never smokers. However, consistent with previous studies we found that smoking exposure in pregnancy is associated with higher BMI and increased odds of being overweight at age four.

The present study was able to detect differences as small as 3% of BMI between children of never smoking mothers and children of mothers who

Conclusions

In this study we found that children of mothers who stopped smoking early in pregnancy did not have increased risk of being overweight at age four years, whereas an increased risk was found among children of women who continued to smoke. Thus, our results further emphasize the importance that pregnant women should quit smoking, at least as soon as they know they are pregnant.

Conflict of interest statement

The authors declare that they have no conflicts of interest.

Role of the funding source

Funding for the PACT study was obtained from the Norwegian Department of Health and Social affairs 1997–2003 and AstraZeneca Norge AS 2000–2001. Grants were obtained from the Norwegian Medical Association and SINTEF Unimed 1999. All authors state independence from the funding sources.

References (34)

  • J.S. Huang et al.

    Prenatal programming of childhood overweight and obesity

    Matern Child Health J

    (2007)
  • A.M. Toschke et al.

    Childhood obesity is associated with maternal smoking in pregnancy

    Eur J Pediatr

    (2002)
  • E. Oken et al.

    Associations of maternal prenatal smoking with child adiposity and blood pressure

    Obes Res

    (2005)
  • A. Chen et al.

    Maternal smoking during pregnancy in relation to child overweight: follow-up to age 8 years

    Int J Epidemiol

    (2006)
  • A. Al Mamun et al.

    Does maternal smoking during pregnancy have a direct effect on future offspring obesity? evidence from a prospective birth cohort study

    Am J Epidemiol

    (2006)
  • J.J. Reilly et al.

    Health consequences of obesity

    Arc. Dis Child

    (2003)
  • K.F. Adams et al.

    Overweight, obesity, and mortality in a large prospective cohort of persons 50 to 71 years old

    N Engl J Med

    (2006)

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