Maternal Smoking and the Risk of Cancer in Early Life - A Meta-Analysis.
BACKGROUND
In spite of the well-known harmful effects on the fetus, many women continue smoking during pregnancy. Smoking as an important source of toxic chemicals may contribute to the developmental origin of diseases.


OBJECTIVE
The aim of this work was to pursue the possible association between maternal smoking and cancer in early life. Specifically, we wanted to identify the associated early life cancer types, and to quantify the associations.


METHODS
In a systematic literature search 825 articles were identified in PubMed and Web of Science, and 55 more through the reference lists. Of these 62 fulfilled the criteria for inclusion in meta-analyses. Using Mantel-Haenszel or DerSimonian and Laird method, depending on heterogeneity of the studies, pooled estimates and 95% confidence intervals for eight cancer types were calculated.


RESULTS
Smoking during pregnancy was associated with an increased risk for for brain and central nervous system tumors (OR = 1.09; 95% CI = 1.02-1.17). Although the risk for lymphoma was also associated (OR = 1.21; 95% CI = 1.05-1.34), it did not hold up in subgroup analyses. Leukemia was not found to be associated with maternal smoking. Five other cancer types (bone, soft tissue, renal, hepatic, and germ cell cancer) were also examined, but the number of studies was too limited to exclude the possibility of maternal smoking as a risk factor for cancer in offspring.


CONCLUSIONS
According to our meta-analyses, maternal smoking is associated with nervous system cancers, but not with leukemia in early life. Confirming or rejecting associations of maternal smoking with lymphoma and the five other cancer types requires further studies.
Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland.|Department of Health Protection, National Institute of Health and Welfare, Kuopio, Finland.
Isabell Katharina
IK
Rumrich
Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland.|Department of Health Protection, National Institute of Health and Welfare, Kuopio, Finland.
Matti
M
Viluksela
School of Pharmacy/Toxicology, Faculty of Health Sciences, University of Eastern Finland, Kuopio Finland.
Kirsi
K
Vähäkangas
Department of Information Services, National Institute for Health and Welfare, Helsinki, Finland and Department of Neurobiology, Care Sciences and Society, Division of Family Medicine, Karolinska Institute, Stockholm, Sweden.
Mika
M
Gissler
Department of Health Protection, National Institute of Health and Welfare, Oulu, Finland.
Heljä-Marja
HM
Surcel
Department of Health Protection, National Institute of Health and Welfare, Kuopio, Finland.
Otto
O
Hänninen
D005260:Female; D006801:Humans; D019369:Life; D009369:Neoplasms / Q000209:etiology*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects / Q000209:etiology*; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*