The Relationships Between Prenatal Smoking Exposure and Telomere Lengths in Fetuses, Infants, and Children: A Systematic Literature Review.

Objective: The aim of this study was to evaluate the relationships between prenatal smoking exposure and telomere lengths (TLs) in fetuses, infants, and children. Methods : This is a systematic review guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Databases searched were Biomedical Reference Collection, MEDLINE via PubMed, CINAHL, PsycINFO, and Google Scholar. The latest search was on October 18, 2019. Results : Seven studies met the inclusion criteria and thus were reviewed. Five of the studies showed significant inverse relationships between prenatal tobacco exposure and TLs in fetuses, infants, and children. One study showed a modification effect of the postconceptual age, indicating that older fetuses with prenatal smoking exposure had shorter TLs than their counterparts. This effect was more prominent after 93 days of postconception. Another study reported a finding that was contrary to the above results, showing that the telomeres of newborns with prenatal smoking exposure were longer than those of their counterparts. Conclusion/Recommendations: This review shows that the impact of prenatal smoking on the health of unborn fetuses, infants, and children is an understudied area. Because of the inconsistent findings and cross-sectional study designs, more research is required, especially longitudinally studies. Nonetheless, the findings of the review provide partial evidence that prenatal smoking can potentially impact the genetic biomarker, TLs, and, thus, health of fetuses, infants, and children. The evidence confirms the current practice that pregnant women should be encouraged to stop smoking as soon as they become pregnant. [ABSTRACT FROM AUTHOR]