Prenatal Effects of Tobacco Exposure

It is particularly dispiriting that despite mounting evidence as to the deleterious effects of maternal tobacco smoking, both pre- and post-natal on the child, mothers continue to smoke. A 2011 publication analyzing data from 1965 to 2008, estimated that anywhere from 22 to 34 percent of American women of reproductive age smoke cigarettes.1 It is thus a major public health concern due to predictable adverse outcomes and neurodevelopmental deficits in offspring.

The effects of pre and post-natal tobacco smoke exposure constitute a long and depressing list that includes2,3

  • sudden infant death
  • lower birth weight
  • small for gestational age
  • otitis media
  • childhood asthma
  • behavioural problems
  • neurocognitive decrease
  • psychological problems
  • deceased lung growth
  • increased respiratory infections

The dangers to the fetus from maternal smoking are long-lasting. Behavioural problems include attention deficit and hyperactivity disorder. Maternal smoking has also been linked to later

  • addiction and conduct disorder
  • obesity
  • cancer
  • increased rates of adolescent smoking
  • lack of aerobic fitness in adolescents4

New research has reinforced the results of prenatal tobacco exposure. The Odds Ratio (OR) for the increased risk of defined outcomes is shown in Figure 1.

Other dangers include genetic changes that alter the connections between brain cells long after birth; epigenetic deregulation; and changes to DNA methylation that remains unaltered over years, making children more susceptible to disease.

Paternal smoking also has long-term effects on the fetus including higher levels of adiposity and increased cardio-metabolic risk factors in both adolescence and adulthood.11 Children of mothers who did not smoke but were exposed to second hand smoke (SHS) during pregnancy were found to have a decrease in gross motor function at age 18 months. There was a significant negative association between the mother’s urine cotinine levels and the child’s motor development.12

There is a glimmer of hope. A recent study involving both parents whose offspring had asthma, found that paternal cessation of smoking during the pregnancy, regardless of the mother smoking, was associated with a decreased risk of childhood asthma.13 It thus becomes absolutely essential to ensure that neither parent smokes and to encourage mothers-to-be to quit smoking, preferably before they get pregnant and to avoid exposure to second-hand smoke.

References

  1. Garrett BE, Dube SR et al. Cigarette smoking - United States, 1965-2008. MMWR Suppl. 2011 Jan 14;60(1):109-13.
  2. DiFranza JR, Aligne CA and Weitzman M.  Prenatal and postnatal environmental tobacco smoke exposure and children's health. Pediatrics. 2004:113 (4 Supp) 1007-15
  3. Bauer T, Trump S et al. Environment-induced epigenetic reprogramming in genomic regulatory elements in smoking mothers and their children. Molecular Systems Biology, 2016; 12 (3): 861 DOI: 10.15252/msb.20156520
  4. Hagnäs MP, Cederberg H, et al. Association of maternal smoking during pregnancy with aerobic fitness of offspring in young adulthood: a prospective cohort study. BJOG: An International Journal of Obstetrics & Gynaecology, 2015; DOI: 10.1111/1471-0528.13789
  5. Chastang J, Baïz N, et al. Postnatal environmental tobacco smoke exposure related to behavioral problems in children. PLoS ONE 2015; 10(8): e0133604. doi: 10.1371/journal.pone.0133604. pmid:26244898
  6. Malloy MH, Kleinman JC, Land GH, Schramm WF. The association of maternal smoking with age and cause of infant death. Am J Epidemiol.1988;128 :46– 55
  7. Niemela S, Sourander A et al. Prenatal nicotine exposure and risk of schizophernia among offspring in a National Birth Cohort. 2016. Am J Psychiatry.  http://dx.doi.org/10.1176/appi.ajp.2016.15060800
  8. Burke H, Leonardi-Bee J et al. Prenatal and passive smoke exposure and incidence of asthma and wheeze: a systematic review and meta-analysis. Pediatrics. 2012 Apr;129(4):735-44. doi: 10.1542/peds.2011-2196
  9. Neuman A, Hohmann C et al. Maternal smoking in pregnancy and asthma in preschool children: a pooled analysis of eight birth cohorts. Am J Respir Crit Care Med. 2012 Nov 15;186(10):1037-43. doi: 10.1164/rccm.201203-0501OC.
  10. Stathis SL, O’Callaghan M, et al. Maternal cigarette smoking during pregnancy is an independent predictor for symptoms of middle ear disease at five years’ postdelivery. Pediatrics.1999;104 :1– 6
  11. Dior U, Lawrence GM et al. Parental smoking during pregnancy and offspring cardio-metabolic risk factors at ages 17 and 32. Atherosclerosis. 2014 Aug; 235(2): 430-437. Published online 2014 Jun 3. doi:  10.1016/j.atherosclerosis.2014.05.937
  12. Evlampidou I, Bagkeris M, et al.  Prenatal second-hand smoke exposure measured with rrine cotinine may reduce gross motor development at 18 months of age. J Pediatr. 2015;167:246-252
  13. Harju M, Keski-Nisula L et al. Parental smoking and cessation during pregnancy and the risk of childhood asthma. BMC Public Health.  2016 May 24;16(1):428. doi: 10.1186/s12889-016-3029-6.