There are very few people in the modern world who would tell you that smoking while pregnant will not negatively affect a growing fetus, or have longer-term implications for developing babies. Even people with lower education and socioeconomic profiles tend to be aware of the risks of smoking during pregnancy. But quitting is difficult for many, and a small proportion of pregnant women continue smoking through gestation. A recent study (see resource 1) conducted by researchers at Brown University found that newborn babies of smoking mothers showed higher rates of irritability (such as colic and excessive crying) and abnormal muscle rigidity (called hypertonicity). The researchers examined 962 mother-baby pairs, and assessed mothers during their prenatal obstetrics visits, and then assessed newborns upon discharge from the hospital. Babies who were premature or who exhibited low birth weights were excluded from the study (by the way, these are very common conditions for mothers who smoke during pregnancy, see resource 2). To assess the babies they had expert doctors rate the babies in terms of their motor reflexes, responses to stimuli, active and passive muscle tone, responses to respiratory challenge, signs of neurologic damage, and irritable behavior, using a method called the Graham-Rosenblith Behavioral Examination. Their results demonstrated that mothers who smoked both moderately and heavily during pregnancy tended to give birth to babies with abnormal muscle rigidity, which hampers proper movement and causes discomfort in the baby, difficulty feeding, and in some rare cases death due to sleep apnea. In mothers who smoked heavily during pregnancy, their babies further showed high rates of irritability and excessive crying. Other work shows that mothers who smoke during pregnancy also tend to have babies with: slow growth in terms of both weight and height through 6-months of age (resource 3), abnormal airway and lung development (resource 4), cleft lip (resource 5), and even childhood leukemia (see resource 6). The moral of the story is to consult local resources and quit smoking before you get pregnant!
1Stroud, L. R., Paster, R. L., Goodwin, M. S., et al. (2009). Maternal smoking during pregnancy and neonatal behavior: A large-scale community study. Pediatrics, 123, 842-848.
2Polakowski, L. L., Akinbami, L. J., & Mendola, P. (2009). Prenatal smoking cessation and the risk of delivering preterm and small-for-gestational-age newborns. Obstetrics and Gynecology, 114, 318-325.
3Fenercioglu, A. K., Tamer, I., Karatekin, G., & Nuhoglu, A. (2009). Impaired postnatal growth of infants prenatally exposed to cigarette smoking. Tohoku Journal of Experimental Medicine, 218, 221-228.
4Hayatbakhsh, M. R., Sadasivam, S., Mamun, A. A., Najman, J. M., & O'Callaghan, M. J. (2009). Maternal smoking during and after pregnancy and lung function in early adulthood: A prospective study. Thorax, in press.
5Leite, I. C., Koifman, S. (2009). Oral clefts, consanguinity, parental tobacco and alcohol use: A case-control study in Rio de Janeiro, Brazil. Brazil Oral Research, 23, 31-37.
6Lee, K. M., Ward, M. H., Han, S., et al. (2008). Paternal smoking, genetic polymorphisms in CYP1A1 and childhood leukemia risk. Leukemia Research, 33, 250-258.