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Can Smoking During Pregnancy (Cause Miscarriage and Stillbirth?

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Updated June 25, 2009

Question: Can Smoking During Pregnancy (Cause Miscarriage and Stillbirth?
Answer:

Smoking during pregnancy is a risky move. For years, doctors have known that women who smoke while pregnant have almost double the risk of having a low-birthweight baby and an increased risk of giving birth prematurely –- and that secondhand smoke exposure carries similar risks. Cigarette smoke can cause numerous health problems in children that last for years after birth, possibly even an increased risk of childhood leukemia.

If that’s not enough to motivate women to avoid cigarettes, evidence is mounting that exposure to cigarette smoke in pregnancy –- even in mothers who don’t smoke -- also increases the risk of miscarriage and stillbirth. Some evidence even indicates that heavy smoking by the father (more than 20 cigarettes a day), possibly even before conception, may also increase the risk of miscarriages.

Theoretically, smoking could cause a miscarriage in a number of ways. In the early days of pregnancy when the baby develops so quickly, cigarette smoke may cause genetic damage in the baby. Chromosomal problems are the most common cause of miscarriages, so it’s theoretically possible that heavy exposure to cigarette smoke could be a cause. Smoking could also change the lining of the uterus to make it harder for the fertilized egg to implant.

If you are wondering how the father’s smoking could affect miscarriages, the answer may lie in the sperm. A few studies have found that men who smoke heavily tend to have increased incidence of sperm with chromosomal abnormalities, and again, chromosomal abnormalities in the developing baby are the most common cause of miscarriages. The answer could also be that the father's smoking causes the mother to be around secondhand smoke, which could theoretically cause problems in the mother's ability to maintain the pregnancy. Future studies will hopefully reveal the exact mechanism behind this link.

Other studies have found an even stronger link between smoking and miscarriages when looking only at miscarriages where the baby was chromosomally normal, however, so the reason why smoking increases miscarriage risks may have nothing to do with chromosmal issues and could have more to do with something else, such as the placenta having a diminished capacity to transport oxygen and nutrients to the fetus. Research indicates that later in pregnancy, smoking does appear to decrease the placenta’s ability to deliver nutrients to the developing baby. In addition to potentially causing miscarriages, this can cause babies to be born with lower birthweight and can also increase the risk of stillbirth, as well as death in the first year of life.

Different studies find different exact figures to indicate the risks of smoking and miscarriage, but regardless of the exact numbers and exact mechanism, quitting smoking or avoiding cigarette smoke is one of the few miscarriage risk factors that you can control. If you smoke and had a past miscarriage, it is impossible to say whether smoking caused your loss or whether it will cause a future miscarriage or stillbirth, but quitting will definitely do you and your future child a favor.

Of course, quitting smoking is no easy undertaking. For help, visit About.com’s guide to Smoking Cessation.

Sources:

George, Lena, Fredrik Granath, Anna L.V. Johansson, Goran Anneren, and Sven Cnattingius, "Environmental Tobacco Smoke and Risk of Spontaneous Abortion." Epidemiology 17(2006): 500-505. Accessed 07 Nov 2007.

Groch, Judity. "Heavy Smoking Compromises Uterine Receptiveness." MedPageToday. 9 Nov 2006.

March of Dimes, "Smoking During Pregnancy." Quick Reference: Fact Sheets. Nov 2004. March of Dimes. 7 Nov 2007.

Venners, Scott A., Xiaobin Wang, Changzhong Chen, Lihua Wang, Dafang Chen, Wenwei Guang, Aiqun Huang, Louise Ryan, John O’Connor, Bill Lasley, James Overstreet, Allen Wilcox, and Xiping Xu. “Paternal Smoking and Pregnancy Loss: A Prospective Study Using a Biomarker of Pregnancy.” American Journal of Epidemiology 159(2004) 993-1001. Accessed 07 Nov 2007.

Wisborg, Kirsten, Ulrik Kesmodel, Tine Brink Henriksen, Sjurdur Frodi Olsen, and Niels Jorgen Secher. "Exposure to Tobacco Smoke in Utero and the Risk of Stillbirth and Death in the First Year of Life." American Journal of Epidemiology 15 Aug 2001 322-327. Accessed 7 Nov 2001.

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