Researchers at Duke Health report that exposure to second-hand tobacco smoke have a lingering effect that can later impair the brain development of a fetus even before conception.

Rats were carefully used in the experiments designed to mimic the second-hand smoke exposures that humans encounter; the researchers found that the chemical components of tobacco smoke affect fetal brain development throughout pregnancy.

Learning, memory and emotional responses are the regions of the brain damaged by second-hand smoke exposure. Despite the mothers were only exposed prior to conception, the effect was most severe with exposures occurring in late gestation.

"This finding has important implications for public health, because it reinforces the need to avoid secondhand smoke exposure not only during pregnancy, but also in the period prior to conception, or generally for women of childbearing age," said Theodore A. Slotkin, Ph.D., professor in Duke's Department Pharmacology & Cancer Biology.

The study was conducted as follow.

• Groups of female rats received the tobacco smoke extract during one of three periods prior to mating, early gestation or late gestation
• The researchers then studied the offspring starting in early adolescence and into adulthood, focusing on brain regions that are known to be adversely affected by nicotine and tobacco smoke.

The researchers express that more studies are needed as it is not known clearly as to how the smoke exposure damages fetal brain development prior to pregnancy.  However, there are potential causes like the lingering effects of some of the smoke components, which can stay in the body for several days after exposure. It is also suggested that the chemicals might change the mother rat's metabolism or hormonal status, or they could be causing an epigenetic alteration in the egg, which affects the activity of genes that control brain function.

"Our study clearly shows there is no stage in which tobacco smoke is innocuous to the developing fetus," Slotkin said. "We warn women about smoking during pregnancy, and most people are aware that secondhand smoke exposure is also harmful to the fetus, but our study is the first to show that exposure prior to conception is potentially damaging, as well. The public health implications should be obvious."

E-cigarettes could also represent a significant hazard for women of childbearing age according to this new finding.

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Duke University Medical Center. Note: you may edit the content for style and length.