The Journal of Pediatrics
Volume 156, Issue 2 , Page 175, February 2010

Magnetic Resonance Imaging Sheds Light on the Nature of Smoking-Induced Effects on Fetal Brain

  • Seppo Heinonen, MD, PhD

      Affiliations

    • Corresponding Author InformationReprint requests: Seppo Heinonen, MD, PhD, Department of Obstetrics/Gynecology, Kuopio University and Kuopio University Hospital, Kuopio, Finland.

Department of Obstetrics/Gynecology, University and Kuopio University Hospital, Kuopio, Finland

Article Outline

MRI, Magnetic resonance imaging

 

See related article, p 185

In this issue of The Journal, Ekblad et al1 report as a part of the PIPARI study the effects of smoking during pregnancy on fetal brain volumes with magnetic resonance imaging (MRI). Specifically, the data are not pregnancy-based but are based on neonatal unit recordings. A subgroup analysis of prenatal exposure to cigarette smoking was carried out in 232 very low birth weight infants, of whom a total of 42 infants were exposed to smoking during pregnancy. The main findings were that the frontal lobe and the cerebellar volumes were significantly decreased in exposed infants without changes in head circumference. The observed differences remained significant after controlling for a number of confounding factors.

The results are interesting for a number of reasons. First, this study now presents solid MRI-based evidence in a clinical setting. We have learned from experimental animal studies that nicotine exerts direct effects on neural cell proliferation, survival, and migration.2, 3, 4 We know from clinical studies on development and cognition that the spectrum of smoking-related impairments in frontal lobe and cerebellar functions include deficits in emotion, impulse control, and attention.5 The study by Ekblad et al1 nicely proposes a link between these observations.

Second, although the mechanisms behind the volumetric changes are beyond the scope of this study, the results show that smoking can damage a fetus at any stage of pregnancy. Smoking in the third trimester has been considered particularly detrimental, but now we know that smoking in the first 2 trimesters can not be considered safe either.6 Interestingly, the specific volumetric changes by MRI were detectable at term age without an obvious effect on head circumference. Once again, it is time to recognize that the lack of evidence is not the same as the evidence of lack.

Third, the incidence of maternal smoking was considerably higher in the cohort and helped the researchers to make the clinical distinction of smoking-related deficits from other causes. The imaging was carried out at term, and therefore the effect of the second-hand exposure to smoking after pregnancy is unlikely to play a major role. On the other hand, maternal smoking is probably only 1 of a number of risk factors that cluster in families. Smoking-related risks are preventable, but the social risk profile remains.

Fourth, there are many interesting questions for the future. The next step would probably be to examine the association between the volumetric changes and behavioral and developmental outcomes in the PIPARI cohort. Furthermore, a similar study would also be worthwhile in term newborns to evaluate whether similar volumetric changes are found among infants born at term. If so, the specific vulnerability of the frontal lobe and cerebellum becomes interesting at the cellular level.

Finally, the study underlines the importance of preventive measures. One more important piece of information from this study is now available to motivate women to quit smoking before pregnancy or, at the latest, when pregnant. Smoking during pregnancy is of concern not only for the increased risk of preterm birth and placental problems such as abruption but also for fundamental effects on fetal brain volumes beginning in early pregnancy. Although there have been major improvements in family planning in recent decades, many pregnancies are still unplanned, and therefore preventive measures should be directed not only to couples planning pregnancy and to child-bearing women right after a positive pregnancy test result but also to all fertile age women and prospective parents.

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References 

  1. Ekblad M, Korkeila J, Parkkola R, Lapinleimu H, Haataja L, Lehtonen L. The PIPARI Study Group maternal smoking during pregnancy and regional brain volumes in preterm infants. J Pediatr. 2010;156:185–190
  2. Roy TS, Sabherwal U. Effects of gestational nicotine exposure on hippocampal morphology. Neurotoxicol Teratol. 1998;20:465–473
  3. Slotkin TA. Cholinergic systems in brain development and disruption by neurotoxicants: nicotine, environmental tobacco smoke, organophosphates. Toxicol Appl Pharmacol. 2004;198:132–151
  4. Levitt P. Prenatal effects of drugs of abuse on brain development. Drug Alcohol Depend. 1998;51:109–125
  5. Obel C, Henriksen TB, Hedegaard M, Secher NJ, Ostergaard J. Smoking during pregnancy and babbling abilities of the 8-month-old infant. Paediatr Perinat Epidemiol. 1998;12:37–48
  6. Rizzo G, Capponi A, Pietrolucci ME, Arduini D. Effects of maternal cigarette smoking on placental volume and vascularization measured by 3-dimensional power Doppler ultrasonography at 11 + 0 to 13 + 6 weeks of gestation. Am J Obstet Gynecol. 2009;200:415;e1-5

PII: S0022-3476(09)00880-4

doi:10.1016/j.jpeds.2009.09.011

Refers to article:

  • Maternal Smoking during Pregnancy and Regional Brain Volumes in Preterm Infants , 12 October 2009

    Mikael Ekblad, Jyrki Korkeila, Riitta Parkkola, Helena Lapinleimu, Leena Haataja, Liisa Lehtonen, The PIPARI Study Group
    The Journal of Pediatrics February 2010 (Vol. 156, Issue 2, Pages 185-190.e1)

The Journal of Pediatrics
Volume 156, Issue 2 , Page 175, February 2010

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