The prenatal period is a sensitive time for fetal growth and development. Maternal life-style related factors during this critical period affects the health and wellbeing of the developing fetus. Specifically, prenatal exposure to tobacco smoke via maternal smoking during pregnancy, increases the risk for respiratory illnesses [1, 2], asthma [3], cleft lip and palate [4] as well as inflammatory polyarthropathies [5] and childhood obesity [6]. Similar to maternal smoking during pregnancy, maternal overweight and obesity is associated with adverse birth outcomes and has been reported in at least one study to exceed smoking as a risk factor with the greatest risk of adverse pregnancy outcomes [7]. While maternal overweight likely affects caries development in the child, the mechanism by which this happens is yet to be elucidated [8].
Development of the primary tooth germ commences at the end of the 5th week of gestation with mineralization starting during the 13th week and continuing on throughout pregnancy to the end of the first year of life for primary teeth and up to 6 years of age for permanent teeth [10]. During this period of tooth development, prenatal exposure to tobacco smoke can negatively affect the quality (i.e. tooth calcification and mineralization) [11] and subsequent timing of tooth eruption [12, 13]. Ntani and colleagues reported that children whose mothers smoked during pregnancy had more teeth erupted at ages 1 and 2 compared to similarly aged children whose mothers did not smoke during pregnancy [13] and suggested that premature tooth eruption likely lie on the causal pathway between maternal smoking during pregnancy and subsequent caries development. In addition, smoking during pregnancy [14], and pregnancy adiposity [9] are associated with low-birth weight and prematurity, factors reported to increase the risk of developmental enamel defects like hypo-mineralization and hypo-calcification [11, 15]. These developmental tooth defects increases tooth susceptibility to cariogenic bacteria [16, 17] in the presence of fermentable carbohydrates [11].
Maternal smoking during pregnancy, exposes the growing fetus to chemical toxins including nicotine through its direct metabolite cotinine which cross the placenta to accumulate in fetal tissues [18]. Furthermore, prenatal exposure to tobacco smoke alters fetal blood flow and protein metabolism, resulting in the accumulation of chemical toxins in the mother and developing fetus [1]. While smoking throughout pregnancy likely increases offspring caries experience, the critical exposure period appears to be the first trimester of pregnancy. Indeed, maternal smoking and weight [8] in the first trimester, were independently associated with increases in subsequent dental caries risk in children [19] and teenagers [8] more so than exposures occurring during other periods of pregnancy. This finding has not been independently replicated in other population groups and there are methodologic limitations on how timing during pregnancy was assessed.

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