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Tobacco and pregnancy: a high-risk combination

The ever-increasing number of women smoking is all the more alarming as tobacco use wreaks havoc before, during and after pregnancy.

Tobacco, fertility and the pill

Tobacco risks
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Prior to pregnancy, tobacco smoking reduces fertility. The average fecundity rate of women who smoke 20 cigarettes daily is 8%, as compared to 22% in non-smoking women.

In addition, women who smoke whilst on the pill are at higher risk of cardiovascular diseases such as myocardial infarction and thrombosis. Nicotine stimulates blood clot formation, damages and shrinks vessel walls. The decrease in oestrogen levels caused by cigarette smoking heightens cardiovascular risks and can lead to premature menopause.

Tobacco smoke is dangerous for your pregnancy

Continuing to smoke during pregnancy entails many risks that have by now been identified by doctors:

  • Higher risk of miscarriage

Chances of ectopic pregnancy are 1.5 times higher in women who smoke up to 10 cigarettes daily and 3 times higher for those who smoke 20 cigarettes a day. Risks increase by a factor of 5 for those who smoke 30 cigarettes per day. Spontaneous abortion rate increases threefold in female smokers. Second-hand smoking also creates additional risks of miscarriage1.

  • Higher risk of preterm delivery

Risks of preterm birth are twice as high in smoking women, even when the amniotic membrane is intact. Chances of premature rupture of membrane (PROM) are twice as high before the end of pregnancy, three times as high prior to the 34th week of amenorrhea2,3,4.

  • Insufficient baby weight upon delivery and impaired child development

The average weight of babies born to smoking women is almost 300g lower than that of babies born to non-smoking women. Moreover, foetal growth delay is twice to three times as common in smoking women5,6,7.

Tobacco smoke is dangerous for your baby

  • Damaged immune system (particularly in cases of infection)

An American study8 has revealed that genetic mutations occur inside the uterus due to tobacco smoking. Expectant mothers who are exposed to their husband’s cigarette smoke during the course of their pregnancy give birth to infants with increased chances of genetic impairment of their immune cells.

  • Elevated risks of sudden infant death syndrome

Nicotine, carbon monoxide and other noxious substances contained in cigarettes pass through the placental barrier, leading to lower amounts of oxygen and nutritional resources being brought to the baby9.  The smoke causes the baby’s heartbeat to accelerate while increasing his or her blood pressure.

You should also note that certain substances resulting from tobacco combustion are very harmful to unborn babies.

Smoking whilst pregnant involves even higher risks for women expecting twins, as evidenced by a study10 conducted by researchers at the University of Michigan.

Chances of sudden infant death syndrome are multiplied by:

-        4, if the mother smoked over the course of her pregnancy;

-        3.4, if the mother smokes 20 cigarettes a day following delivery and if the father doesn’t smoke;

-        7.4, if both parents smoke more than 20 cigarettes a day.

  • Elevated risk of illness

Children born to smoking mothers have higher risks of respiratory and ENT infection, as well as increased chances of suffering from asthma.

After pregnancy, other consequences of tobacco intoxication may afflict young mothers. The average amount of breast milk produced by a smoker is 690ml, as against 960ml in non-smoking mothers. There is also a correlation between the number of cigarettes smoked and the quantity of nicotine in maternal milk.

Need more reasons not to smoke during pregnancy?

“Though it’s true that pregnant women have a higher incentive to quit smoking, 25% of them continue to smoke despite being pregnant” admits Gilbert Lagrue, head of the Center of Tobacco Studies at the Chenevier Hospital in Créteil, France. He goes on to say that “we use the same methods with these women as we do with any smoker: though we know babies hate nicotine, substitutes such as patches are preferable to cigarette smoke, which contains hundreds of other toxic substances.”

However, half of women who manage to quit smoking in the course of their pregnancy resume smoking after childbirth. You’ll likely need to fight out of your smoking addiction, but remember you’re doing for your child’s sake as well as your own.

1. Centers for Disease Control, Center for Health Promotion and Education, Office on Smoking and Health, 1988.
2. Bull WHO 1987; 663-737
3. Epidemiol Rev 1993; 15: 414-443.
4. Am J Obstet Gynecol 1998;179: 1051- 1055.
5. N Engl J Med 1985;312:82-90.
6. Pediatrics 1990;86:176- 183.
7. BMJ 1994 October;309:901
8. Nature Medicine, vol. 4, p. 1144-51.
9. BMJ 1992; 304: 265-266
10. Am J Public Health. 2000 Mar; 90(3):395-400.

Posted 30.07.2010


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