Attention, moms! If you needed another reason to not smoke while pregnant or breastfeeding at this point, here it is. A recent study published in the journal Human Reproduction has revealed that mothers who smoke when they are pregnant or breastfeeding have significantly damaged their son’s future fertility. This research only adds to growing evidence suggesting the negative consequences that come with smoking while pregnant for both mothers and their children.

"It would be unethical to deliberately expose pregnant mothers and their offspring to the toxins in cigarettes — we already know that smoking in pregnancy harms the baby in the womb — as babies are often born small and vulnerable to disease,” Professor Eileen McLaughlin, co-director of the Priority Research Center in Chemical Biology at the University of Newcastle in Australia, said in a statement. “So, in this study we used a mouse animal model, which directly mimics human smoking, to look at what effects the mothers smoking during pregnancy and breastfeeding has on the fertility of their male pups."

McLaughlin and her colleagues fitted 27 female mice with nose pieces that were attached to a machine pumping in smoke. This piece of machinery was meant to mimic the way human inhale smoke via cigarettes. Mice inhaled the equivalent of 24 cigarettes a day in humans for a period of six weeks. A control of 27 mice were exposed to same conditions, but with normal air instead of smoke. All female mice mated with males and “smoking” mice continued to smoke through pregnancy and lactation.

The 108 male offspring from both “smoking” and “non-smoking” female mice were examined for damage to the DNA of cells that produce sperm, sperm count, the shape of sperm, and the mobility of sperm. Researchers also tested each male offspring’s ability to produce their own offspring in adulthood. Findings revealed that male offspring of “smoking” female mice were significantly less likely to have a large sperm count, normally shaped sperm, mobile sperm, or sperm that could bind to eggs during in vitro fertilization compared to the male offspring of “non-smoking” female mice.

"Our results show that male pups of 'smoking' mothers have fewer sperm, which swim poorly, are abnormally shaped and fail to bind to eggs during in vitro fertilisation studies,” McLaughlin explained. “Consequently, when these pups reach adulthood they are sub fertile or infertile. This is the first time we have been able to prove conclusively that male baby exposure to cigarette toxins in pregnancy and early life will damage later life fertility," McLaughlin said.

McLaughlin concludes that smoking cessation campaigns should continue to push for expecting mothers to give up smoking during pregnancy and breastfeeding. Although smoking while pregnant is considered taboo, McLaughlin estimates that around 25 percent of young women still smoke while pregnant and/or breastfeeding. She also referenced recent studies on men in their 30s and 40s with poor sperm health, who were born when smoking while pregnant or breastfeeding was less frowned upon.

According to Child Trends, expecting mothers who smoke expose their children to far more dangerous health concerns than infertility, including premature birth, low birth weight, stillbirth, and infant mortality. The children of smoking mothers are three times more likely to die from Sudden Infant Death Syndrome. Even mothers exposed to secondhand smoke run the risk of giving birth to a child with a lower weight which can lead to other adverse health concerns.

"We now know that exposure to cigarette toxins directly affects the stem cell population in the testes, causing a permanent reduction in the population of sperm produced,” McLaughlin added. “We also know that oxidative stress induced by these toxins causes damage to the nuclei and mitochondria (the cell's 'power' supply) of cells in the testes and this results in sperm with abnormal heads and tails, that are unable to swim properly or successfully bind and fuse with eggs.”

Source: Sobinoff A, McLaughlin E, et al. Damaging legacy: maternal cigarette smoking has long-term consequences for male offspring fertility. Human Reproduction. 2014.