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EFFECTS OF SMOKING DURING PREGNANCY AND
THE EFFECTS ON THE PEDIATRIC PATIENT.
Rachel Alcorn
Laura Wooldridge
AHEC Community Project
May 25, 2007
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TABLE OF CONTENTS
Introduction . . . . . . . . . . . . . . . . . . . pg. 3
Effects of smoking during pregnancy. . . . . . . . pg. 3
Toxic chemicals of smoking . . . . . . . . . . . . pg. 5
Infertility. . . . . . . . . . . . . . . . . . . . pg. 6
Malformations of the embryo. . . . . . . . . . . . pg. 7
Spontaneous abortion . . . . . . . . . . . . . . . pg. 7
Placenta previa-accreta. . . . . . . . . . . . . . pg. 8
Placenta abruptio. . . . . . . . . . . . . . . . . pg. 9
Growth restriction and SGA . . . . . . . . . . . . pg. 9
Ectopic pregnancy. . . . . . . . . . . . . . . . . pg. 10
Stillbirth and infant mortality. . . . . . . . . . pg. 11
Maternal smoking and the pediatric patient . . . . pg. 12
Maternal smoking and low birth weight. . . . . . . pg. 12
Risk of cleft lip and palate deformity . . . . . . pg. 13
Nicotine withdrawal and the newborn. . . . . . . . pg. 14
Sudden infant death syndrome . . . . . . . . . . . pg. 15
Smoking as a cause of asthma . . . . . . . . . . . pg. 17
Attention-deficit/hyperactivity disorder . . . . . pg. 19
Smoking cessation in the pregnant patient. . . . . pg. 20
Conclusion . . . . . . . . . . . . . . . . . . . . pg. 21
References . . . . . . . . . . . . . . . . . . . . pg. 22
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INTRODUCTION
Approximately 17.6 percent of women between the ages
of 15 and 44 years old smoked during their pregnancy last
year as stated by the Centers for Disease Control (CDC,
2007). Our purpose in this paper is to discuss the major
effects of smoking tobacco during pregnancy and in the
pediatric patient to show the importance of smoking
cessation. In this paper we aim to show in detail how
smoking during pregnancy affects the pathological
development of the fetus, the effects of the fetus itself,
as well as the long-term effects on the newborn and the
child. We will also discuss how to safely quit smoking
during pregnancy and some of the benefits of smoking
cessation on pregnancy and childhood outcomes.
EFFECTS OF SMOKING DURING PREGNANCY
It has long been known that smoking is bad for your
health, but when you add a growing fetus to the picture the
risks related to tobacco use increase tremendously. One
study states that 27.2 percent of women of reproductive age
are smoking. It is proposed that the side effects of
smoking are dose-related, meaning the more cigarettes
smoked daily the higher the risk, however any amount of
smoking will raise the probability of complications
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occurring during and after pregnancy. In addition to the
commonly studied side effects of lung disease and bladder
cancer, cigarettes can have devastating effects on a
pregnant mother and her baby. The compounds in cigarettes
have been found to decrease the fertility of men and women
making it harder to conceive. The chemicals also have a
profound effect on a growing baby; it has been proven that
smoking causes structural and vascular defects leading to
spontaneous abortion, placental and fallopian tube changes,
intrauterine growth restriction (IUGR) and premature
rupture of membranes (PROM). Women who choose to smoke
during pregnancy are taking a chance with two lives and
should be encouraged to quit or at least cut back
significantly during their pregnancies (Hammoud, et al.
2005).
Numerous studies have shown that the amount of
cigarettes smoked greatly increases the risk of side
effects to the mother and the baby. A study found that the
rate of preterm delivery in smokers increased from 6.9
percent in women who smoked up to 5 cigarettes daily to 8.9
percent in women who smoked more than 10 cigarettes daily.
This trend remains true for IUGR, APGAR scores and PROM.
For this reason if the patient is unwilling or unable to
quit, it is important to stress the need for them to reduce
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the number of cigarettes smoked on a daily basis (Hammoud,
et al. 2005).
TOXIC CHEMICALS OF SMOKING
Smoking is toxic to a growing baby due to the
various compounds found in cigarettes. The most toxic
chemicals are carbon monoxide, nicotine, cyanide as well as
89 carcinogens. Of the 89 carcinogens some of the common
ones include arsenic, benzene, cadmium, chloroform,
formaldehyde, lead, styrene and urethane. These substances
have been studied and found to cause various cancers and
fetal malformations.
Carbon monoxide attaches more readily to hemoglobin
and myoglobin than oxygen which decreases the amount of
circulating oxygen, as well as stored oxygen, in the body.
Decreased oxygen delivery to the fetus causes hypoxia which
then inhibits proper growth and development of the fetus.
Nicotine easily crosses the placenta and actually reaches
levels 15 percent higher in the amniotic fluid and fetus
than the mother experiences. With levels of nicotine being
increased in the fetus a newborn baby actually experiences
nicotine withdrawal.
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abnormalities in their sperm as a result of smoking
(American Society for Reproductive Medicine, 2003).
MALFORMATIONS OF THE EMBRYO
Harmful environmental stimuli are most detrimental
during the organogenesis stages of pregnancy. Nicotine is
a major teratogen that can severely impair proper growth
of the embryo because it accumulates in fetal blood and in
the amniotic fluid. It has been postulated that nicotine
causes cell death in the embryo resulting in spontaneous
abortion or fetal malformations. The mechanism of nicotine
on the cells leads to oxidative stress which is a major
factor in programmed cell death. Therefore, nicotine is
causing apoptosis in embryonic cells. When embryos are
exposed to 3M of nicotine they develop neural tube
defects and have shorter crown-rump lengths. The effects
are more pronounced with increased amounts of nicotine
exposure, which confirms other studies of dose-related
effects of nicotine (Zhao, 2005).
SPONTANEOUS ABORTION
Spontaneous abortion is a result of the embryo not
implanting or growing properly in the uterus. Smoking has
serious vascular effects on the uterus that cause
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vasoconstriction of the vessels. The main structural
changes in the placenta involve the villous capillaries.
The capillaries become tortuous and poorly branched which
impedes blood flow and nutrient delivery to the fetus. In
addition, vasoconstriction reduces blood flow to the uterus
and placenta. Without blood the fetus is unable to get the
proper nutrients to grow, which can lead to a spontaneous
abortion. Decreased blood flow to the placenta actually
causes hypertrophy of the placenta as a compensatory
mechanism. The trophoblastic basal lamina of the placenta
will thicken while the fetal capillaries are reduced in
size. The enlarged placenta grows enough to cover the
internal cervical os resulting in placenta previa. Another
complication to the placenta is peripheral necrosis due to
the decreased blood flow. Necrosis of the outer tissue will
weaken the walls of the placenta and may result in an
abruption. Other structural changes include increased
calcifications and fibrin deposits in placentas exposed to
smoke (Van Meurs, 1999).
PLACENTA PREVIA - ACCRETA
Placenta previa is a condition that occurs late in
pregnancy. The placenta implants too close to the cervical
os and can partially or completely cover the cervical os.
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Placenta accreta is a condition of the placenta attaching
too deeply to the uterine wall but does not penetrate the
uterine muscles. It is common to have both placenta previa
and accreta occurring at the same time. Both conditions may
result in third trimester bleeding, preterm delivery and
death to fetus and mother. The risks of developing either
condition increases with smoking during pregnancy. The
incidence of placenta accreta was 12.2 percent compared to
4.8 percent in nonsmokers due to the hypertrophy of the
placenta. The risk of placenta previa and accreta increases
with each subsequent pregnancy because of scarring which
leads to fewer implantation sites (Usta, et al., 2005).
PLACENTA ABRUPTIO
Placenta abruptio is the condition of premature
separation of the placenta from the uterus. This causes
painful bleeding during the third trimester. For each year
of smoking the risk of abruption increases by 40 percent
and 25 out of 100 cases of abruptio are linked to smoking
(Usta, et al., 2005).
GROWTH RESTRICTION AND SGA
As discussed earlier, fetal hypoxia can lead to IUGR.
The average birth weight of a term baby is 2500 grams. A
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baby that has been exposed to cigarettes weighs an average
of 90-200g lighter at term than babies who are not exposed.
Pringle, et al shows that weight, length and head
circumference were all decreased at birth in babies exposed
to smoking in utero compared to non-exposed babies.
Ultrasound found no significant reduction in head,
abdominal circumference or fetal length at 20 weeks
gestation; however, the changes were noted at 30 weeks
gestation and were still evident at birth. They also found
that insulin-like growth factor was significantly lower in
cord plasma of babies exposed to smoke. The placental
weight was also reduced in the babies. This reduction was
dose dependant; mothers who smoked 20 cigarettes daily had
placentas that were 400 grams lighter than mothers who did
not smoke (Pringle, et al., 2005).
ECTOPIC PREGNANCY
Ectopic pregnancies are the primary cause of death in
the first trimester of pregnancy to the mother. Common
causes of ectopic pregnancies are pelvic inflammatory
disease, tubal surgeries and a history of infertility.
However, with the increase in the number of women who
smoke, there have also been increases in the number of
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ectopic pregnancies. As discussed earlier the components of
cigarettes have many negative effects.
These toxins also have an effect on tubal motility as
discussed by Handler, Davis, Ferre and Yero. They measured
wave amplitude of tubal contractions before and after
smoking and found that nicotine exposure caused decreased
uterotubal activity and longer periods of inactivity. In
addition to the effects the nicotine has on tubal activity,
the idea that smoking also reduces immunity has brought up
questions about the increase in pelvic inflammatory disease
and the effects it has on tubal infections. Overall it was
found that smoking increases the risk of ectopic
pregnancies twofold compared to nonsmokers and the amount
of risk is dose related (Handler, et al., 1989).
STILLBIRTH AND INFANT MORTALITY
Still birth occurs when a fetus dies in utero or
during labor and is then delivered. The chances of having a
still birth double with nicotine exposure in the womb. The
mechanism of death is most likely due to growth retardation
as a result of hypoxia from excess carbon monoxide in the
blood. Women who stop smoking greatly decrease their
chances of having a still birth and if they can stop
smoking by their 16th week of pregnancy 25 percent of all
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still births could be prevented (American Society for
Reproductive Medicine, 2003).
MATERNAL SMOKING AND THE PEDIATRIC PATIENT
The effects of maternal smoking on the infant can lead
to many abnormalities including low birth weight, cleft
palate, nicotine withdrawal and an increased incidence of
sudden infant death syndrome (SIDS), asthma and attention-
deficit/hyperactivity disorder (ADHD). Many of these
problems occur due to the chemistry of nicotine and how it
affects the vasculature in utero and the effects it has on
the development of the lungs and neurotransmitters in the
brain.
MATERNAL SMOKINGAND LOW BIRTH WEIGHT
Smoking during pregnancy can double a womens risk of
having a baby at low birth weight and 12 percent of babies
born to smokers were of low weight (less than 2500 grams).
As discussed earlier maternal smoking during pregnancy can
cause intrauterine growth restriction which can lead to
lower birth weights in the newborn. Low birth weight
infants account for 7.6 percent of all live births and most
of these are caused by smoking. Many of these infants will
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die since approximately 69 percent of all infant deaths are
due to low birth weight (Law, 2003).
Nicotine causes vasoconstriction of the arteries in
the body which leads to decreased flow and is the major
cause of myocardial infarction and cerebral vascular
accidents in the United States. Low birth weight is caused
by the same pathology. There is a decreased amount of
oxygenated blood going to the placenta due to the
vasoconstriction of the arteries when the mother smokes
which leads to poorer nutrition and inability to grow in
utero. These infants do no develop fully, having increased
risks for future problems including sudden infant death
syndrome and asthma.
RISK OF CLEFT LIP AND PALATE DEFORMITY
Cleft lip and palate are the fourth most common birth
defects in the world and account for 1 of every 700
newborns. During fetal development the palate is normally
formed during the fourth to seventh weeks of gestation with
fusion occurring at the ninth week of gestation. When this
closure fails, a cleft palate or lip results. This is
characterized by an incomplete fusion of the lip or hard
palate which disables the infant in their ability to
breathe and eat. If left uncontrolled, long term speech and
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hearing loss can occur. Cleft palate babies will require
approximately 10 to 20 surgeries throughout their lives to
have full function of their mouths; even then they will
still have scarring and most likely be left with a speech
impediment (Chung, 2000).
Studies have shown that the more cigarettes the mother
smokes the higher the risk for cleft palate deformity,
again the dose-dependent theory. The thought is behind how
the chemicals in the cigarettes alter the transforming
growth factor-alpha gene variants. Transforming growth
factors are important because they play crucial roles in
the development of embryonic tissues, epithelial cells,
tissue regeneration and regulation of the immune system.
When the chemicals of the cigarettes alter the transforming
growth factors, it delays or inhibits the growth of the
embryonic tissues in utero and leads to malformations of
the infant (Shaw, 1996).
NICOTINE WITHDRAWAL IN THE NEWBORN
A mother who smokes during pregnancy has many things
to worry about with her child; however, nicotine withdrawal
most likely is not one of them. Just as in cocaine, heroin
and alcohol use during pregnancy the fetus builds up an
addiction to these chemicals. When the chemicals are
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suddenly taken away the infant starts to crave them and
go through withdrawal. Some of the withdrawal symptoms the
infant will encounter are insomnia, headache, stomach pain,
constipation and gas. These can all lead to a very unhappy
and inconsolable infant.
When it comes to the heavier drugs more severe forms
of withdrawal proceed, as in seizures and electrolyte
abnormalities. When an infant becomes addicted to nicotine
the results are similar for why it is so hard for people to
quit smoking. The number of nicotinic receptors in the
brain are increased immensely which leads for more and more
of them requiring nicotine to stay calm. When they do not
receive the nicotine, the infant becomes more agitated and
excitable.
When mothers smoke the chemicals cross the placenta
and act as vasoconstrictors reducing uterine blood flow by
up to 38%. This results in fetal hypoxia and brain and
neuronal damage (Law, 2003). This is also the cause of the
infant having a higher risk of attention-
deficit/hyperactivity disorder, which is discussed later.
SUDDEN INFANT DEATH SYNDROME
Sudden infant death syndrome, or SIDS, is defined as
death of an infant unexplainable by postmortem exam. SIDS
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is fairly common, being two of every 1000 children born in
the United States. This commonly occurs in children under 6
months of age, more commonly between the hours of 4AM-6AM
and is the most commonly unexplained cause of death before
the age of one (Auth, 2006).
The actual cause of SIDS is unknown; however, there
are many hypothesized reasons with the main one being the
inability to wake oneself when hypoxia occurs. When infants
feel they are out of oxygen and stop breathing, receptors
in the brain trigger what is called autoresuscitation.
When this fails the infant is unable to awaken and take a
breath. One of the major risk factors for impaired
autoresuscitation is the effects of nicotine and how it
raises the arousal threshold in the infant so they are
unable to wake up, turn their head and gasp for air. This
risk is greatly increased with second hand smoke continued
in the home after nicotine exposure in utero (Thompson,
2006).
Other risks factors of SIDS include sleeping in the
prone position, low birth weight, low socioeconomic status,
drug-addicted mothers and family history of SIDS. Even with
these other risk factors smoking cessation while pregnant
and after birth, studies have shown a great decrease in the
incidence of SIDS.
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SMOKING AS A CAUSE OF ASTHMA IN THE PEDIATRIC PATIENT
Asthma is a major cause of hospital emergency room
visits in the young patient. Asthma is a reversible type
lung disease that is caused by a triad of obstruction,
hypersensitivity of airways and inflammation. There is
initially inflammation of the smooth muscle layer of the
trachea, then large amounts of mucus are secreted in
response to some allergen and as the eosinophils and
lymphocytes travel to the area, a greater amount of
obstruction occurs leading to an asthma attack.
It is well known that secondary cigarette smoking
leads to acute asthma attacks because of bronchial
irritation and inflammation. Asthma can be caused by other
triggers such as household allergens, pollen, mold, mildew,
extreme temperatures and pet dander. However, recent
studies have shown that mothers who smoke during pregnancy
cause a higher risk for their child to acquire asthma
usually within the first 3 years of life. It was found that
Children with any in utero exposure to maternal smoking
were at increased risk of asthma (Li, 2005).
Many of these children that are exposed to tobacco in
utero are also exposed in their homes after birth; however,
one study has proven that the risk of in utero tobacco
exposure and environmental exposure are independent
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variables in the cause of asthma and both are of equal
risks in causing asthma. As explained in the American
Journal of Respiratory and Critical Care Medicine, smoking
during pregnancy causes many dangerous carcinogens to cross
the placenta and harm the development of the lungs
(Gilliland, 2001). The lungs start to develop around 6-8
weeks gestation and in a healthy full-term fetus are
completed before birth. This means at the critical
developmental times, if the mother is smoking the ability
for the lungs to mature correctly is hindered. This leads
to lower surfactant levels which decreases the ability of
the lungs to expand and contract. The alteration of
development leads to lower lung function in general and
increased bronchial hyperactivity (Gilliland, 2001).
The factors that cause asthma are bronchial
irritation, inflammation, and spasm. It makes sense that
over activity of the smooth muscles due to the chemical
exposure from smoking is a high risk factor for asthma.
Therefore, tobacco smoke is not only a trigger for an
asthma attack it is also linked with the cause of asthma.
In the research it is estimated that if mothers did not
smoke while pregnant there would be an overall reduction in
asthma by approximately 15 percent (Gilliland, 2001).
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ATTENTION-DEFICIT/HYPERACTIVITY DISORDER AND SMOKING
Attention-deficit/hyperactivity disorder, or ADHD, is
on the rise in the United States. ADHD is defined as a
pattern of behavior where the child is inattentive or
hyperactive, but most commonly a mix of the two.
Inattentive type features short attention span, inability
to listen or follow instruction, forgetfulness, inability
to organize and easily distracted. Hyperactive type is
classified as being fidgety, difficulty staying seated or
waiting in line, impulsive speech and inability to remain
quiet. There must be six of the above symptoms for
classification and they must last at least 6 months with
the diagnosis before 7 years old (Auth, 2006).
There are many speculations of what is causing this
disorder in children, as in parental neglect, lack of
discipline and other environmental factors. One theory is
that mothers who smoke while pregnant increase the risk of
ADHD. Studies have shown that there is a threefold
increased risk for having offspring with hyperkinetic
disorder with mothers who smoked while pregnant compared
with those who did not (Schmitz, 2006). The physiology
behind these facts is that nicotine reduces cerebral blood
flow to the brain which leads to a low birth weight,
microcephaly and abnormalities in the neuronal matter of
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the body and result in lower IQs. This in turn is expressed
as a hyperactive child that is unable to pay attention in
class and mentally does not have the capability of higher
level thinking. These children also have a higher number of
nicotinic receptors in the brain, as do adults who smoke
and are much more easily agitated than a child not exposed
to nicotine in utero (Schmitz, 2006).
SMOKING CESSATION IN THE PREGNANT PATIENT
As discussed in this paper there is a high importance
in smoking cessation of the pregnant patient. This needs to
be a goal set as early as possible in the pregnancy or when
planning a pregnancy. The first process as with all other
smokers who are trying to quit; the 5 As which are Ask,
Advise, Assess, Assist, and Arrange. First ask about
thoughts of smoking cessation, advise on the long-term
effects to the infant and mother, assess the willingness to
quit, assist the mother in quitting and arrange for a stop
date and other help that may be necessary.
However, the help that we can actually give other than
emotional support and counseling to the pregnant mother may
be greatly limited. Studies have not shown whether the risk
or benefit is higher in using nicotine replacement in the
pregnant patient. The American College of Obstetricians and
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Gynecologists, ACOG, recommends that nicotine patches and
gum should only been used in the pregnant patient when
counseling has failed and nicotine nasal spray and inhaler
should be avoided since it is a Category D and may cause
harm to the developing fetus. Bupropion should again only
be used if counseling has failed; this is a Category B drug
and has not been shown to cause actual harm to a human
fetus (Bailey, 2002). With these limited techniques in
smoking cessation of the pregnant patient strong, early
counseling is the first line therapy.
CONCLUSION
Smoking during pregnancy has multiple consequences on the
outcome of the child. From time of conception to early
childhood, the chemicals found in cigarettes play an
integral part in the development and well-being of fetus
and child. Multiple studies have consistently shown that
cigarettes cause complicated pregnancies which include
infertility, placenta previa and abruption, spontaneous
abortion, fetal malformations and later can lead to
fetal/infant deaths, developmental delays and childhood
asthma. In many cases smoking cessation before conception
or in early gestation will avoid many of the harmful
effects discussed in this paper.
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