Smoking Before, After Pregnancy Harms Daughters' Fertility

By Madeline Vann
HealthDay Reporter
Thursday, November 22, 2007; 12:00 AM

Copyright © 2007 ScoutNews, LLC. All rights reserved.

WEDNESDAY, Nov. 21 (HealthDay News) -- 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 retrospective 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 Canadian 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, according to the researchers. 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.

"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," explained lead researcher Dr. Andrea Jurisicova.

Further analysis indicated that the effects of PAHs on the number of follicles in female offspring were mediated through a receptor that affects the expression of a gene that makes a protein that causes cells to die. The researchers then demonstrated similar effects in human ovarian tissue transplanted into immunocompromised mice.