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
About the author – Ana EspinoPhD in Immunology, specialized in Virology
