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Q: I know that I'm not supposed to smoke when I'm pregnant (and I will quit when that happens), but will smoking affect my chances of getting pregnant?
A: Let's get the smoke out of your eyes. Women who smoke are 60 percent more likely than nonsmokers to be infertile. (Put into more statistical terms, studies have shown that the relative risk of infertility in women smokers is 1.60, compared to the baseline of 1.0 for nonsmokers).
This detail has been “smoked out” from an analysis of 12 pertinent studies that included 10,928 female smokers, who were compared to 19,179 women who did not smoke. Not only were the smokers less fertile but it was also found that they experienced a 42 percent increase in conception delay of over one year when compared to those who were cigarette free. These adverse effects of smoking on fertility have been found to occur in women who smoked “just” a few cigarettes a day. The higher the number of cigarettes the longer it took them to get pregnant and the higher their rate of infertility problems.
Medical researchers say that there are several pathways in which smoking can prevent a woman from getting pregnant (Maybe it's nature's way of encouraging us to change our destructive habits before delivering a child):
- Egg depletion: Menopause occurs one to four years earlier in smoking women than non-smoking women, since smoking accelerates ovarian egg (oocyte) death. Various toxins have been identified in the ovary and the fluid around the egg in smokers, which may indeed kill the fragile oocytes.
- Sperm damage: Smoking doesn't just affect the vulnerability of the egg; we also know that gene damage can occur in sperm when tobacco-smoke constituents bind to the sperm's DNA. Gene-damaged sperm are less likely to do their job.
In a world where we don't want to wait to get pregnant, many women turn to assisted reproductive technology (ART) after one year of trying to conceive — smoking has a skull and bones effect even if ART is used. One study showed that if a woman smokes in her lifetime, failure to conceive with ART doubled. (And the longer a woman smoked the greater the failure rate for ART...increasing as much as 9% per year of previous smoking.)
To add insult to tobacco injury, smoking is also associated with increased spontaneous miscarriages in both natural and assisted pregnancies. One study has shown that smoking accounts for 16 percent of miscarriages. We know that in addition to nicotine; carbon monoxide and cyanide in the inhaled cigarette smoke passes through the placenta and into the fetus. This can cause constriction of the blood vessels in the placenta, lack of blood flow, and miscarriage at an early stage, or fetal growth restriction and death at a later stage of pregnancy.
In a recent review article on smoking and infertility by the Practice Committee of the American Society for Reproductive Medicine, they found:
- Available biological, experimental, and epidemiological data shows that 13 percent of infertility may be attributable to smoking.
- Smoking appears to accelerate the loss of reproductive performance and may advance menopause by one to four years.
- Smoking is associated with a risk of spontaneous abortions (miscarriages) and ectopic pregnancies.
- A mutation in the DNA of the egg or sperm is one possible mechanism for how smoking may affect pregnancy and reproductive performance.
- Many studies show that smokers require nearly two times as many in vitro fertilization (IVF) attempts as nonsmokers.
- Semen parameters (qualities) and the results of sperm function tests are poorer in smokers (though smoking has not been conclusively shown to decrease male fertility).
- The effect of exposure to smoke in the environment is now established and nonsmokers with excessive exposure may suffer reproductive consequences as great as those as smokers (that's pretty scary).
Dr. Reichman’s Bottom Line: There are so many reasons not to smoke. If you want to get pregnant, then definitely don't smoke. A cigarette (or a few) a day can keep a baby away.
Dr. Judith Reichman, the TODAY show's medical contributor on women's health, has practiced obstetrics and gynecology for more than 20 years. You will find many answers to your questions in her latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," which is now available in paperback. It is published by William Morrow, a division of HarperCollins.
PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.