Smoking Before And After Pregnancy Harms Daughters' Fertility

Main Category: Smoking / Quit Smoking
Also Included In: Pregnancy / Obstetrics;  Fertility
Article Date: 22 Nov 2007 - 15:00 PDT

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Researchers have identified the chemical pathway by which a mother's smoking before and after pregnancy might reduce her daughter's fertility by as much as two-thirds.

Cigarette smoking during pregnancy has been shown in studies to affect the fertility of a woman's offspring, but this is the first study to offer an explanation of the biology behind the effect, the scientists claim.

A team at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto investigated the impact of polycyclic aromatic hydrocarbons (PAH), a byproduct of smoking, on mouse fertility.

Researchers injected three groups of female mice with a low-dose mixture of PAH: One group received PAH before conception and again when they were providing milk for their pups; one group received PAH only before conception; and the third group received PAH only during lactation. A fourth control group did not receive PAH but were mated at the same time as the others.

The total amount of PAH given to each mouse over the three-week injection cycle was equivalent to 25 packs of cigarettes. The exposed mice did not have fewer pups in their own litters, but when researchers investigated the number of eggs in their female offspring, they found about 70 percent fewer follicles available to produce eggs.

Dr Andrea Jurisicova lead author, explained, "Mothers, mice in this case, exposed to PAHs, (environmental pollutants found in cigarette smoke, car exhaust, smoke produced by fossil fuel combustion, as well as in smoked food) before pregnancy and or during breast-feeding, but not during pregnancy, can cause a reduction in the number of eggs in the ovaries of their female offspring by two-thirds. This limits the window in which the daughter will be able to reproduce."

Dr Norman Edelman said, "This study now is providing a chemical pathway, which is very nice. The new data provides biological support for epidemiological results, such as the previously observed reduction in fertility among daughters of smoking women."

Although the findings do not define the length of time between quitting smoking and healthier fertility in offspring, Jurisicova noted that previous studies have shown that women who smoke have better results with in vitro fertilisation one year after they quit smoking. The mice in the current study conceived up to two weeks after their final PAH injection, which is approximately equivalent to three menstrual cycles in women.

The effect of a mother's cigarette smoking is not limited to her female children. A study published in the Jan. 1 issue of the American Journal of Epidemiology suggested that the male offspring of mothers who smoke have lower sperm counts.

There is still more research to be done, Jurisicova noted.

She added, "We hope to continue studying the female offspring to see if they enter the mouse version of menopause earlier than mice whose mothers were not exposed to PAHs. We also hope to study if their reduced fertility passes on to subsequent generations, and if the granddaughters are predisposed to similar problems."

http://www.ash.org.uk

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