Why Does Smoking Affect Your Eggs?by Miles Britton
Study after study has shown the adverse effects that cigarette smoking has on a woman's reproductive system. Especially at risk are the fragile egg cells inside a woman's ovaries known as oocytes. The chemicals found in cigarette smoke can mutate the DNA of these egg cells, leading to reproductive and fertility problems. Besides nicotine, a highly addictive chemical, cigarette smoke contains a number of other dangerous and poisonous chemicals, such as carbon monoxide, formaldehyde, cyanide and arsenic.
Women are born with around 1 million to 2 million oocytes, the egg cells that potentially develop into mature eggs, in their ovaries. These egg cells die off at varying rates throughout a woman's life due to a process called follicular atresia. By the time a women reaches sexual maturity and begins to ovulate, she has roughly 400 eggs that will be released once a month during her reproductive years. A woman will begin menopause when the number of oocytes falls below a certain threshold.
According to a 2007 report by MSNBC, smoking increases a woman's chance of infertility by 60 percent. Women who smoke also increase their chance of a delayed conception of over 1 year by 42 percent. These effects were found in women who smoked only a few cigarettes a day, though women who smoked more had increased trouble getting pregnant and a higher rate of fertility problems. The report also noted that 16 percent of miscarriages are due to smoking.
In a report published in the Biology of Reproduction in 2005, scientists at the University of California, Riverside found that cigarette smoke can disrupt the way eggs are transported. When female hamsters were exposed to cigarette smoke, their eggs were significantly less likely to be transported by the oviduct, or the fallopian tubes. This was because chemicals in the smoke cause the eggs to get stuck in the upper part of the fallopian tubes, making it difficult for the cilia, the hair-like projections that line the interior of the tubes, to move the eggs to the point where fertilization occurs.
Cigarette smoke is a known mutagen, an agent that causes mutations in DNA. DNA mutation occurs when the nucleotide sequence of the DNA is damaged or changed in some way, often due to mutagens. The chemical benzo[a]pyrene (B[a]P) is one of the more potent carcinogenic chemicals in cigarette smoke, one that can cause damage during oocyte cell division and lead to DNA mutation. Unlike sperm, though, oocytes have the ability to repair DNA damage before fertilization.
In 2007, researchers at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto discovered that polycyclic aromatic hydrocarbons (PAHs), a group of chemicals found in cigarette smoke, accelerate the destruction of oocytes. PAHs are formed when certain types of smoke cause molecules to fragment into unstable arrangements, which then recombine into carcinogenic compounds. While there is some scientific debate over whether women can reproduce more egg cells later in life, early loss of these egg cells can lead to early menopause and infertility. The study also discovered that resveratrol, an antioxidant found in wine and grape skins, has the ability to counteract the adverse effects of PAH on oocytes, but it is only effective in amounts much larger than you could get from consuming grapes or wine.