Does smoking during pregnancy protect against type 1 diabetes?

By Ana Espino | Published on November 24, 2025 | 3 min read


Type 1 diabetes (T1D) is a chronic autoimmune disease caused by the destruction of the β-cells of the pancreatic islets of Langerhans, leading to lifelong dependence on insulin. Its global prevalence is steadily increasing, particularly in developed countries, making T1D a major public health concern due to its metabolic and psychosocial complications.

Although genetic susceptibility is a key factor, early environmental exposures may influence its onset. Among these, maternal smoking during pregnancy is receiving growing attention. Despite its well-known harmful impact on fetal development (growth restriction, respiratory and neurodevelopmental disorders), its association with T1D remains controversial.  

A previous meta-analysis suggested an inverse association between prenatal smoking and T1D risk, but it relied mainly on retrospective studies prone to bias. The aim of this study was therefore to reassess this association using only prospective cohort studies, providing greater methodological robustness.    

What if smoking actually reduced the risk?  

A total of 5.9 million children were included in the analysis, based on rigorous criteria: birth to mothers whose smoking status during pregnancy was documented, and longitudinal follow-up until the possible onset of type 1 diabetes (T1D) before age 18. The primary outcome measure was the relative risk (RR) of developing T1D according to prenatal exposure to tobacco.  

The overall analysis highlights a significant inverse association between maternal smoking during pregnancy and the risk of type 1 diabetes (T1D) in the child. This relationship remains stable in sensitivity analyses, even when each study is excluded one at a time, strengthening the robustness of the results.

Subgroup analyses confirm the consistency of the effect regardless of:

• cohort size (< or >150,000 children),
• method of T1D diagnosis (clinical criteria or ICD coding),
• or the prevalence of prenatal smoking.  

However, the lack of adjustment for maternal diabetes reduces the apparent magnitude of the protective effect, suggesting the presence of residual confounding.  

Really fewer cases of T1D among children of mothers who smoke?  

Type 1 diabetes (T1D) is a rapidly rising autoimmune disease of childhood, caused by destruction of the pancreatic cells that produce insulin. Although genetics play a role, they do not fully explain this continuous increase. Several studies have explored the role of maternal smoking during pregnancy, but most are retrospective, with often contradictory results and methodological biases. This study was initiated to reassess the T1D-smoking relationship and guide future research.  

The results show a significant inverse association, suggesting a lower risk of T1D in children exposed in utero. This relationship proved robust and consistent across different analyses, regardless of the context of the included studies. However, it remains counterintuitive and must be interpreted with caution. Tobacco is a well-established risk factor for numerous fetal and neonatal complications.   The observed effect could result from a transient immunomodulatory mechanism related to nicotine or from epigenetic modifications affecting the fetal immune system. It is also possible that the association is influenced by unmeasured confounding factors, such as socioeconomic status, certain parental behaviors, or genetic predispositions.

Read next: Tobacco: a deeper addiction than it seems