Secondhand smoke has long been shown to have ill effects on health, but now, researchers have found that exposure prior to pregnancy can still have an effect on fetal brain development later on should a woman get pregnant.

For a study published in the journal Toxicological Sciences, researchers from Duke University Medical Center used an animal model to show that the effects of secondhand smoke exposure linger to affect fetal brain development in a later pregnancy.

Specifically, they found that secondhand smoke exposure damages brain regions involved with emotional responses, memory, and learning. And while effects are most severe in exposures occurring during late gestation, they were still present even when a mother was exposed to secondhand smoke prior to conception.

"This finding ... 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 study author Theodore A. Slotkin.

Studying The Effects Of Secondhand Smoke Exposure

Slotkin and colleagues simulated exposure to secondhand smoke by capturing it and then extracting its chemical compounds. Once the chemical compounds were isolated, they were then administered via a solution to lab animals implanted with pumps. This eliminated stress associated with breathing in smoke, which the researchers say in itself has the potential to affect brain development in fetuses.

Female rats used in the study were grouped into three depending on when they were administered extracts of tobacco smoke: before mating, early gestation, and late gestation. The resulting offspring were then observed beginning in their early adolescence until they were adults. The researchers focused on observing brain regions known to be affected adversely by tobacco smoke and nicotine.

According to the researchers' findings, tobacco smoke exposure in all three of the rat groups resulted in offspring with impaired function in their cholinergic brain circuits, or the parts of the brain responsible for memory and learning, as well as the serotonin circuits, or the parts of the brain that function to regulate emotional behavior and mood.

Secondhand Smoke Exposure Before Pregnancy

It's not clear with the researchers how exactly secondhand smoke exposure prior to pregnancy is able to affect fetal brain development so they are highlighting the need for further study. However, one of the potential causes they came up with was that the lingering effect is due to tobacco smoke's chemical compounds remaining in the body long after exposure.

Additionally, they suggested that the chemicals may have altered the mother's hormonal status or metabolism, or that the alterations occurred within eggs themselves, which affected gene activity associated with controlling brain function.

According to Slotkin, what their study highlights is that there is no point in time where tobacco smoke could be considered not harmful to a fetus in development. Smoking during pregnancy and secondhand smoke in general have been known to be bad for the health, but the study is the first to establish that exposure to tobacco smoke prior to a conception can also be damaging to a fetus' developing brain.

An earlier study from the researchers noted that nicotine is to blame for a significant portion of the effects attributed to tobacco smoke. As such, e-cigarettes also present dangers to women who are of childbearing age.

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