MedicalResearch.com Interview with:
Nis Brix M.D., PhD Student
Department of Public Health
Department of Epidemiology
Aarhus University Hospital
MedicalResearch.com: What is the background for this study? What are the main findings?
Response: Several studies have indicated a secular trend towards earlier puberty. This is a potential concern as early puberty has been linked to an increased risk of a number of diseases, such as obesity, diabetes, cardiovascular diseases and certain types of cancer. For this reason, our research team are interested in identifying potential modifiable causes of early puberty.
Smoking during pregnancy may be such a modifiable cause of early puberty in the children. Former studies have already linked smoking during pregnancy to earlier age at the daughters’ first menstrual period, a relatively late marker of pubertal development, but other markers of puberty are less studied, especially in the sons.
We studied 15,819 sons and daughters. The mothers gave detailed information on smoking during their pregnancies, and the children gave information on a number of pubertal milestones half-yearly from the age of 11 years. The milestones for the sons were age at voice break, first ejaculation of semen, pubic hair and testicular growth, armpit hair growth and onset of acne. For the daughters the milestones were age at their first menstrual period, pubic hair growth, breast development, armpit hair growth and onset of acne.
Our results suggested that the more cigarettes the mother smoked during her pregnancy the earlier her children, both sons and daughters, went through puberty. If the mother smoked more than ten cigarettes a day during pregnancy, the children appeared to go through puberty, on average, three to six months earlier than the children of non-smoking mothers.
MedicalResearch.com: What should readers take away from your report?
Response: It is known that smoking is harmful to the unborn fetus. Smoking is, among other things, associated with an increased risk of low birth weight, premature birth and increased mortality. There are thus a wide range of other good reasons to give up smoking before pregnancy. We hope that our results can be used as another motivating factor to stop smoking among women who are planning on becoming pregnant.
MedicalResearch.com: What recommendations do you have for future research as a result of this work?
Response: It would be interesting to look deeper into the potential mechanisms at play. A lot of work has already been done on this topic. Smoking during pregnancy has been linked to an altered hormonal balance in the fetus, to altered growth patterns in the child, and to epigenomic changes (i.e., reversible changes to the DNA that may change the expression of genes) in the newborn child. All these factors, or their interplay, have the potential to explain the earlier puberty observed in children of smoking mothers.
MedicalResearch.com: Is there anything else you would like to add?
Response: The main strength of the study was the large number of children studied and the use of several pubertal milestones. A limitation of the study was that it relied on self-reporting of the mother’s smoking during her pregnancy and self-reporting of the children’s pubertal milestones.
I would like to thank for the opportunity to discuss our research. I have no disclosures to report.
Nis Brix, Andreas Ernst, Lea L B Lauridsen, Erik T Parner, Jørn Olsen, Tine B Henriksen, Cecilia H Ramlau-Hansen. Maternal Smoking During Pregnancy and Timing of Puberty in Sons and Daughters: A Population-Based Cohort Study. American Journal of Epidemiology, 2018; DOI: 10.1093/aje/kwy206
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