Tobacco smoking and pregnancy is related to many effects on health and reproduction, in addition to the general health effects of tobacco. A number of studies have shown that tobacco use is a significant factor in miscarriages among pregnant smokers, and that it contributes to a number of other threats to the health of the fetus.[1][2] Second-hand smoke appears to present an equal danger to the fetus, as one study noted that "heavy paternal smoking increased the risk of early pregnancy loss."[3]
Ideally, women should not smoke before, during or after pregnancy. If this is not possible, however, the daily number of cigarettes must be reduced to a minimum to minimize the risks for both the mother and child. This is particularly important for women in undeveloped countries where breastfeeding is essential for the child’s overall nutritional status.[4]
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Smoking can adversely affect the ability of individuals to conceive and bear children. It is important to examine these effects because smoking before, during and after pregnancy is not an unusual behavior amongst the general population and can have detrimental health impacts, especially among both mother and child as a result. It is reported that roughly 20% of pregnant women smoke at some point during the three months prior to conception (see fertilization) and delivery (see childbirth).[5]
Tobacco use has been shown to cause erectile dysfunction (ED) in men.[6] Organic causes of erectile dysfunction can include cardiovascular diseases and diabetes, neurological problems, hormonal insufficiencies and drug side effects. Nicotine and anti-depressants are the two most common drugs which interfere with erectile function and dysfunction as a result of these causes is known as “drug-induced male sexual dysfunction". There are numerous drug therapies to counteract erectile dysfunction. However, the least controversial treatment is the cessation of smoking and the use of other tobacco products.
Smoking decreases fertility levels in both women and men. Female smokers are 60% more likely to have female infertility than female non-smokers.[7] Male smokers also have approximately 30% higher odds of male infertility than male non-smokers.[8] There is increasing evidence that the harmful products of tobacco smoking kill sperm cells.[9][10]
In the United States today, approximately 10% of women smoke during pregnancy (March of Dimes. 2010. Smoking During Pregnancy.)[11] Of women who smoked during the last 3 months of pregnancy, 52% reported smoking 5 or less cigarettes per day, 27% reported smoking 6 to 10 cigarettes per day, and 21% reported smoking 11 or more cigarettes per day.[12] In the United States, women whose pregnancies were unintended are 30% more likely to smoke during pregnancy than those whose pregnancies were intended.[13]
Smoking during pregnancy can lead to a plethora of health risks to both the mother and the fetus. Smoking can cause
Smoking cigarettes doubles a woman's risk of developing placental problems. These conditions, as stated above, include premature rupture of membranes, placenta previa, and placental abruption.
Early rupture of membranes means that the amniotic sac will rupture prematurely, and will induce labor before the baby is fully developed. Oftentimes this will not be lethal to the fetus or the mother, but it would cause severe economic stress as the premature child would have to stay in the hospital to gain health and strength to be able to sustain life on its own.
Placenta previa is when the placenta implants over the opening of the cervix. Having a placenta previa is especially dangerous as the baby would not be able to be born vaginally. If it when the placenta would rupture before the baby was birthed,causing the mother to hemorrhage. Having placenta previa is an economic stress because it insists upon having a caesarean section delivery, which is more expensive and requires a longer recovery period in the hospital.
An ectopic pregnancy is when the fetus implants itself outside of the uterus. This could prove fatal to the mother, and will be fatal to the fetus. The most common place for the fetus to implant is in the Fallopian Tubes. The Fallopian Tube could burst if the fetus becomes too large and is not caught in time.
Finally, placental abruption is the premature separation of the placenta from the attachment site. This again can cause problems to both the mother and the fetus. The mother could lose large amounts of blood and hemorrhage. The fetus could be put in distress because it cannot receive the proper amount of nutrients or oxygen, and the placental abruption could cause the fetus’ death. Babies born to women who smoke during pregnancy also have roughly 30% higher odds of being born prematurely.[12]
Smoking can also impair the general development of the placenta. Impairing placental development is problematic because it reduces blood flow to the fetus. If the placenta is not developing fully, the umbilical cord (which transfers oxygen and nutrients from the mother's blood to the placenta) cannot do its job fully. If the umbilical cord cannot transfer enough oxygen and nutrients to the fetus, it will not be able to fully grow and develop.[14] These conditions can result in heavy bleeding during delivery that can endanger mother and baby, although cesarean delivery can prevent most deaths.[11]
There is limited evidence that smoking reduces the incidence of pregnancy-induced hypertension,[15] but not when the pregnancy is with more than one baby (i.e. it has no effect on twins etc.).[16] Smoking does, however, increase the likelihood of almost every other pregnancy-related health risk to both mother and child, and is the single most preventable cause of illness and death among mothers and infants in the developed world.[17]
Smoking nearly doubles the risk of low birthweight babies. In 2004, 11.9% of babies born to smokers had low birthweight as compared to only 7.2% of babies born to nonsmokers. More specifically, infants born to smokers weigh on average 200 grams less than infants born to women who do not smoke.[12] Premature and low birthweight babies face an increased risk of serious health problems as newborns have chronic lifelong disabilities such as cerebral palsy (a set of motor conditions causing physical disabilities), mental retardation and learning problems. Overall, they also face an increased risk of death.[11]
Sudden infant death syndrome (SIDS) is the sudden death of an infant that is unexplainable by the infant’s history. The death also remains unexplainable upon autopsy. Infants exposed to smoke, both during pregnancy and after birth, are found to be more at risk of SIDS due to the increased levels of nicotine often found in SIDS cases.[18] Infants exposed to smoke during pregnancy are up to three times more likely to die of SIDS that children born to non-smoking mothers.[11]
A 2003 study showed that babies born to mothers who smoked during pregnancy often undergo withdrawal-like symptoms similar to babies born to mothers who used illicit drugs during pregnancy. These babies tend to be more jittery and are harder to soothe than babies born to non-smokers.[11]
| Defect | Odds ratio |
|---|---|
| cardiovascular/heart defects | 1.09 |
| musculoskeletal defects | 1.16 |
| limb reduction defects | 1.26 |
| missing/extra digits | 1.18 |
| clubfoot | 1.28 |
| craniosynostosis | 1.33 |
| facial defects | 1.19 |
| eye defects | 1.25 |
| orofacial clefts | 1.28 |
| gastrointestinal defects | 1.27 |
| gastroschisis | 1.50 |
| anal atresia | 1.20 |
| hernia | 1.40 |
| undescended testes | 1.13 |
| hypospadias | 0.90 |
| skin defects | 0.82 |
| All defects combined | 1.01 |
Smoking can also cause other birth defects, reduced birth circumference, altered brainstem development, altered lung structure, and cerebral palsy.[5] Recently the U.S. Public Health Service reported that if all pregnant women in the United States stopped smoking, there would be an estimated 11% reduction in stillbirths and a 5% reduction in newborn deaths.[11]
A recent study has proposed that maternal smoking during pregnancy can lead to future teenage obesity. While no significant differences could be found between young teenagers with smoking mothers as compared to young teenagers with nonsmoking mothers, older teenagers with smoking mothers were found to have on average 26 percent more body fat and 33 percent more abdominal fat than similar aged teenagers with non-smoking mothers. This increase in body fat may result from the effect smoking during pregnancy, which is thought to impact fetal genetic programming in relation to obesity. While the exact mechanism for this difference is currently unknown, studies conducted on animals have indicated that nicotine may affect brain functions that deal with eating impulses and energy metabolism. These differences appear to have a significant effect on the maintenance of a healthy, normal weight. As a result of this alteration to brain functions, teenage obesity can in turn lead to a variety of health problems including diabetes (a condition in which the affected individual’s blood glucose level is too high and the body is unable to regulate it), hypertension (high blood pressure), and cardiovascular disease (any affliction related to the heart but most commonly the thickening of arteries due to excess fat build-up).[20]
Studies indicate that smoking during pregnancy increases the likelihood of offspring beginning to smoke at an early age.[5]
Quitting smoking at any point during pregnancy is more beneficial than continuing to smoke throughout the entire 9 months of pregnancy, especially if it is done within the first trimester (within the first 12 weeks of pregnancy). A recent study suggests, however, that women who smoke anytime during the first trimester put their fetus at a higher risk for birth defects, particularly congenital heart defects (structural defects in the heart of an infant that can hinder blood flow) than women who have never smoked. That risk only continues to increase the longer into the pregnancy a woman smokes, as well as the larger number of cigarettes she is smoking.[11] This continued increase in risk throughout pregnancy means that it can still be beneficial for a pregnant woman to quit smoking for the remainder of her gestation period.[14] There are many resources to help pregnant women quit smoking such as counseling and drug therapies. For non-pregnant smokers, an often-recommended aid to quitting smoking is through the use of Nicotine replacement therapy in the form of patches, gum, inhalers, lozenges, sprays or sublingual tablets (tablets which you place under the tongue). However, it is important to note that the use of Nicotine Replacement Therapies (NRTs) is questionable for pregnant women as these treatments still deliver nicotine to the child. For some pregnant smokers, NRT might still be the most beneficial and helpful solution to quit smoking. It is important to talk to your doctor to determine the best course of action on an individual basis.[21]
Infants exposed to smoke, both during pregnancy and after birth, are found to be more at risk of sudden infant death syndrome (SIDS).[18]
If one does continue to smoke after giving birth, however, it is still more beneficial to breastfeed than to completely avoid this practice altogether. There is evidence that breastfeeding offers protection against many infectious diseases, especially diarrhea. Even in babies exposed to the harmful effects of nicotine through breast milk, the likelihood of acute respiratory illness is significantly diminished when compared to infants whose mothers smoked but were formula fed.[22] Regardless, the benefits of breastfeeding outweigh the risks of nicotine exposure.
Passive smoking is associated with many risks to children, including, sudden infant death syndrome (SIDS),[23][24], asthma[25][26], lung infections,[27][28][29][30] impaired respiratory function and slowed lung growth,[31] Crohn's disease,[32] learning difficulties and neurobehavioral effects,[33][34] an increase in tooth decay,[35] and an increased risk of middle ear infections.[36][37]