Effect of prenatal or perinatal nicotine exposure on neonatal thyroid status and offspring growth in rats

Smoking during pregnancy causes intrauterine growth retardation and low birth weight of the offspring. However, it is unclear whether nicotine, rather than other compounds from a cigarette, would mediate long-term growth retardation. There is a body of evidence suggesting that optimal thyroid status is important for the normal development of the fetus. Therefore, these studies examined whether developmental nicotine exposure would interfere with the growth of the offspring and alter the thyroid status of neonates. Pregnant Sprague-Dawley rats were given 0, 15 or 25 mg nicotine pellets throughout pregnancy. Some offspring continued to receive 1 or 2 mg/kg/day nicotine during early postnatal period. The remaining offspring received no further treatment after birth. The body weight of all offspring was monitored until adulthood. Additionally, the neonatal thyroid status from all treatment groups was assessed from the serum of 10-day-old pups. Regardless of the timing of nicotine exposure, the nicotine treatment significantly increased the body weight in female offspring starting on postnatal day (PD) 35 and such an increase persisted into adulthood (PD 91). However, this nicotine exposure paradigm led to a transient increase in male offspring body weight on PD 35. Furthermore, current nicotine exposure regimens did not alter the total T4 level, T3 uptake and the calculated Free T4 index. The present findings are in agreement with some clinical studies reporting a higher body weight among children born to mothers who smoked during pregnancy. Furthermore, the data on thyroid status suggest that cigarette smoking-induced alterations in thyroid status might be mediated through compounds in cigarettes other than nicotine.