Systematic Review Assesses the Association between Maternal Smoking during Pregnancy and Dental Development

Conditions affecting orofacial development can significantly impact the quality of life. Identifying and understanding potential causes is critical for proper patient education and early intervention strategies for parents and affected infants.¹

Environmental and maternal exposures to noxious agents, in addition to genetic variations, are known to disrupt molecular pathways, causing defects in tooth morphology and agenesis. Maternal smoking during pregnancy (MSDP), a recognized human teratogen, increases the risk of adverse health outcomes and can lead to developmental disorders characterized by changes in the craniofacial complex. Tooth development begins around the sixth week in utero and continues throughout gestation and the first year of life. Disturbances during these phases of development could potentially affect tooth number, shape, and mineralization.¹

The four main stages of the development of the tooth germ in utero include:¹

1. 1. Initiation stage: starts at 6 weeks
   2. Bud stage: around 8 weeks
   3. Cap stage: around 9 weeks
   4. Bell stage: around 11 weeks

The eruption of primary teeth can vary, but typically begins between 6–10 months and is completed by 33 months. Permanent teeth typically begin to erupt around age 6 and continue to erupt until about 12 years of age (excluding third molars). The crowns of primary teeth complete mineralization by one year, while permanent teeth complete crown formation between 8–9 years old. Root formation for all teeth continues for 2–3 years after they erupt.¹

If something disrupts tooth development during these critical stages, the effects might not be evident until later and often require radiographs or clinical exams to detect the defect. For instance, disruption in the initiation stage could lead to congenitally missing teeth. In comparison, disruption during the bell stage could affect tooth size, shape, or cusp location. Other concerning outcomes include enamel hypomineralization and abnormal eruption patterns.¹

Although the basics of tooth development are generally understood, there is still limited research on how MSDP impacts specific dental defects. MSDP has been associated with tooth decay and cleft lip/palate. However, its role in other issues, such as hypodontia, short root anomaly, irregular tooth eruption, molar incisor hypomineralization, and other enamel defects, remains poorly understood.¹

MSDP has long been recognized as a public health concern. It is associated with an increased risk of low birth weight, preterm birth, miscarriage, and ectopic pregnancy. However, research directly evaluating MSDP as a primary factor in dental abnormalities has been limited and inconsistent.¹

Due to these uncertainties, a systematic review aimed to “comprehensively assess current literature to determine whether MSDP has a direct effect on the development of teeth, focusing on anomalies such as deviations in root and crown shape, tooth number, hard tissue mineralization, and eruption patterns.”¹

The Review

The research question posed for this systematic review was “What is the effect of smoking during pregnancy on the occurrence of dental development conditions in offspring when compared to non-smoking controls?”¹

The study designs included in the review were observational studies, including cross-sectional, longitudinal/cohort, and case-control studies. All studies were conducted on human participants and published between 2000 and July 2024. Inclusion criteria required studies to assess a dental developmental outcome and include groups of participants who smoked and participants who were non-smokers. The age range for offspring inclusion was 0–19 years.¹

Six electronic databases were searched: MEDLINE, Embase, CINAHL, Scopus, Web of Science, and Maternity and Infant Care (MIC). A total of 17 articles published between 2007 and 2023 were included in the final review.¹

Studies were divided into groups based on the outcome assessed. Of the included studies, 6 evaluated the effect of MSDP on molar incisor hypomineralization, 3 assessed enamel defects other than molar incisor hypomineralization, 2 assessed hypodontia, 5 assessed eruption timing, and 1 assessed short root anomaly. The number of participants was based on the number of offspring evaluated. This varied between studies from 102–5536.¹

Most of the included studies evaluated smoking at any stage of pregnancy. Only 2 studies assessed smoking during specific trimesters. Of the 17 studies, 15 recorded smoking as a binary yes or no, while 2 studies reported the number of cigarettes smoked during pregnancy.¹

Seven of the studies did not mention any adjustments made for confounding factors in their final analysis. The other studies adjusted for multiple confounding factors, including sex, age, socioeconomic status, and some prenatal and perinatal maternal factors.¹

The Results

Associations between MSDP and enamel defects, as well as hypodontia, were identified in this review. However, the quality of the evidence was low, and some studies indicated a potential association with molar incisor hypomineralization.¹

Molar Incisor Hypomineralization

Six studies evaluated whether MSDP is associated with molar incisor hypomineralization in children. The results were mixed, with an equal number of studies demonstrating an increased incidence or a significant association as those showing no association. Two studies found a statistically significant difference between the presence of molar incisor hypomineralization in children of mothers who smoked versus those who did not smoke during pregnancy. Additionally, one study found an increased incidence, determining the risk was twice as high (OR = 2, 95% CI 0.8–4.4). However, this finding had a wide confidence interval (CI), which means the possibility that there is no association cannot be ruled out.¹

Yet, 3 other studies found no clear connection between MSDP and molar incisor hypomineralization. One of these studies found that after adjusting for confounders, the association disappeared. The evidence for molar incisor hypomineralization in children associated with MSDP is inconclusive.¹

Enamel Defects Other than Molar Incisor Hypomineralization

Three studies evaluated MSDP and enamel defects other than molar incisor hypomineralization, with the focus on enamel hypoplasia. All 3 studies found an association between MSDP and enamel hypoplasia.¹

One of the 3 studies evaluated the effects of smoking based on trimester. The results indicated that smoking during the second and third trimesters was significantly associated with enamel hypoplasia. However, when the second and third trimesters were combined and analyzed without adjusting for other factors, the association was not significant. It was only after a second model was used that included birth vitamin D data as a covariate that a significant association was found. Additionally, the results indicated that smoking only in the first trimester was not significantly associated with enamel hypoplasia.¹

The second study examined both enamel hypoplasia and enamel opacities as dental outcomes. The study results indicated that only enamel hypoplasia had a significant association with MSDP, while opacities were not significantly associated.¹

The third study found a significant association between MSDP and the overall presence of enamel defects in children when compared to those whose mothers did not smoke.¹

Hypodontia

Two studies evaluated the risk of hypodontia associated with MSDP. Both studies examined the dose-dependent relationship between smoking and hypodontia. One study found that smoking at any level during pregnancy was associated with an increased risk of hypodontia, but only smoking 10 or more cigarettes per day was statistically significant. The other study found a statistically significant association with smoking 6 or more cigarettes per day, though a similar observation was not present in the group that smoked 1–5 cigarettes per day. Both studies determined there was an increased risk of hypodontia within the parameters of their definition of heavy smoking.¹

The dose-dependent relationship between the number of cigarettes smoked and hypodontia strengthens evidence of a causal relationship rather than simply an association.¹

Eruption

Five studies evaluated the association between MSDP and eruption pattern or time. These studies had mixed results. Most studies included found no significant association. However, one study found that children of mothers who smoked during pregnancy had their first tooth erupt earlier and had more teeth by age one when compared to children of non-smoking mothers.¹

Short Root Anomaly

One study evaluated the association between MSDP and short root anomaly. This study found a significant association between MSDP and short root anomaly. Children of mothers who smoked during pregnancy were 5 times more likely (OR: 4.95; 95% CI: 1.65–14.79) to have short root anomaly when compared to children of non-smoking mothers. However, this finding had a wide confidence interval; therefore, it should be interpreted with caution.¹

Limitations and Strengths

Overall, the studies used in this systematic review had multiple limitations, including low-quality evidence, methodological limitations, indirectness, imprecision, inconsistency, and publication bias. A meta-analysis could not be completed due to a high degree of variability or heterogeneity.¹

This study also had strengths, including the incorporation of a range of different dental developmental conditions and the extensive search strategy.¹

Conclusion

Current evidence presents a plausible mechanism between MSDP and dental anomalies, which indicates that oxidative stress and placental hypoxia may be key factors in the development of dental anomalies among children whose mothers smoked during pregnancy.¹

Chronic fetal hypoxia associated with nicotine exposure may cause developmental delays, leading to disruption of proper tooth development. Additionally, nicotine can disrupt the deposition of enamel and dentin matrices, potentially leading to poor mineralization of the tooth structure. This mechanism could be the cause of the increased incidence of hypodontia and enamel defects among children of mothers who smoke.¹

Identifying risk factors, such as MSDP, is vital for improving dental care. However, the current research has limitations that reduce the applicability of the findings in clinical practice.¹

To improve future research, the authors offer multiple suggestions. First, they recommend the use of standardized methods to measure both smoking and dental anomalies. Second, include when during pregnancy smoking occurred and how many cigarettes were smoked. Third, use biomarkers instead of self-reporting to confirm smoking status. Fourth, conduct prospective cohort studies instead of retrospective studies to reduce bias. Lastly, control for other factors, like passive smoking exposure, genetics, and maternal health.¹

This review shows that smoking during pregnancy is associated with dental problems like hypodontia and enamel defects in children. But due to inconsistent methods, the strength of this evidence is limited. Better-designed studies are needed to confirm these risks and guide clinical care.¹

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Reference

1. Tiernan, H., Masud, M., Lange, S., et al. The Association between Maternal Smoking during Pregnancy and Dental Development in Offspring: A Systematic Review. Evid Based Dent. Published online May 29, 2025. https://www.nature.com/articles/s41432-025-01168-x