Aim

To investigate the impact of partner smoking on maternal cotinine levels during pregnancy.

Hypotheses

Comparison of the magnitude of association of maternal and paternal smoking during pregnancy is a useful method for assessing whether smoking during pregnancy may have an intrauterine effect on offspring outcomes. (1) This has been used in ALSPAC to investigate the impact of smoking during pregnancy on offspring birthweight, blood pressure, trajectories of height and adiposity and attention deficit hyperactivity disorder. (2-4) This method assumes that the effect of passive smoking in utero on offspring of mothers who do not smoke but have partners who smoke is minimal. However, recent work in ALSPAC has demonstrated that maternal smoking is strongly associated with cotinine (a metabolite of nicotine) levels in non-smoking offspring during childhood and adolescence. (5) Therefore, it is possible that exposure to household smoking may be an important determinant of health outcomes. If this is the case, it may be necessary to control for this in comparisons of the effect of maternal and paternal smoking on offspring outcomes.

We aim to investigate the extent to which partner smoking affects maternal cotinine levels during pregnancy. Associations between partner smoking and maternal cotinine will be investigated using linear regression, stratified by self-reported smoking status of the mother. In addition, we will look at associations of partner smoking with cotinine in all mothers, adjusted for maternal smoking status and heaviness. It may be necessary to use cotinine cut offs to validate maternal self-reported smoking status.

Exposure variables

Paternal smoking status and heaviness

Stratify by maternal smoking status

Outcome variables

Maternal cotinine measured during pregnancy

Confounding variables

Age

Maternal BMI

1. Smith GD. Assessing intrauterine influences on offspring health outcomes: can epidemiological studies yield robust findings? Basic & clinical pharmacology & toxicology. 2008;102(2):245-56. Epub 2008/01/30.

2. Howe LD, Matijasevich A, Tilling K, Brion MJ, Leary SD, Smith GD, et al. Maternal smoking during pregnancy and offspring trajectories of height and adiposity: comparing maternal and paternal associations. International journal of epidemiology. 2012;41(3):722-32. Epub 2012/03/13.

3. Langley K, Heron J, Smith GD, Thapar A. Maternal and Paternal Smoking During Pregnancy and Risk of ADHD Symptoms in Offspring: Testing for Intrauterine Effects. American Journal of Epidemiology. 2012;176(3):261-8.

4. Brion MJ, Leary SD, Smith GD, Ness AR. Similar associations of parental prenatal smoking suggest child blood pressure is not influenced by intrauterine effects. Hypertension. 2007;49(6):1422-8. Epub 2007/04/04.

5. Stiby AL, Macleod J, Hickman M, Yip V, Timpson N, Munafo M. Association of Maternal Smoking With Child Cotinine Levels. Nicotine & tobacco research : official journal of the Society for Research on Nicotine and Tobacco. 2013.