Objective: To assess the impact of maternal smoking during pregnancy (MSDP) on the neonatal hypothalamic-pituitary-adrenal axis.
Study design: In a prospective observational study, salivary cortisol and cortisone levels were measured at the fourth day of life during resting conditions and in response to a pain-induced stress event in healthy neonates whose mothers smoked cigarettes during each stage of pregnancy and compared with controls.
Results: Neonates in the control group (n=70) exhibited a physiologic stress response with a significant increase in cortisol (1.3 to 2.1 ng ml-1; P<0.05) and cortisone (11.8 to 17.8 ng ml-1; P<0.05) from baseline levels, whereas in neonates from mothers who smoked (n=33), cortisol (0.9 to 0.8 ng ml-1; P=0.77) and cortisone (11.5 to 13.0; P=0.19) stress response was not significantly different from baseline levels. A two-way analysis of variance confirmed these findings in both groups.
Conclusions: Healthy neonates whose mothers smoked during pregnancy show a blunted stress response on the fourth day of life. Thus, MSDP leads to a dysregulation of the HPA axis with continued effects in neonatal life. This might explain long-term consequences of MSDP such as overweight, diabetes mellitus and modification of blood pressure control mechanisms in adult life.