Smoking adversely affects the fetus and newborn. The effects of smoking are lessened if the mother quits smoking before or during early pregnancy.
Cigarette smoke contains 68000 toxic substances, including nicotine and hydrogen cyanide and toxic heavy metals such as lead and arsenic, all of which readily gain access to the mother’s circulation and cross the placenta. Cyanide lowers the fetus’s ability to use vitamin B12, which is vital to protein formation and the formation of red blood cells. Carbon monoxide which is produced by cigarette smoke and car exhaust, rapidly enters the bloodstream, firmly attaching itself to the red blood cells and preventing the uptake of oxygen. This causes the fetal haemoglobin to be artificially elevated. Carbon monoxide diffuses across the placenta, reaching levels in the fetus that may exceed the mother’s by 10 to 15%. Studies show that babies of smokers have monoxide levels that lead to approximately a 20% reduction in their blood levels of oxygen. Cases of birth defects and brain damage have been noted in laboratory animals when carbon monoxide levels are extremely high. It is felt that humans must be exposed to very high levels before these effects would occur; however, there is no known safe limit of carbon monoxide exposure.
Nicotine causes blood vessels to constrict, contributing to hypertension. The body elevates the blood pressure and the heart beats faster in an effort to counteract the loss of blood volume. This, combined with the decrease in oxygen carrying capacity of the red cells, can lead to mild angina pectoris (chest pain on exertion). The rapid drop in uterine and placental blood flow caused by constriction of maternal vessels causes the baby’s heart rate to rise in an effort to maintain oxygen levels. During ultrasound exams, maternal smoking has also been noted to decrease fetal breathing movements. Insufficient oxygen is dangerous for the fetus, especially during labour when the blood flow to the uterus is diminished during contractions.

Cholesterol and platelet adherent properties are both increased in smokers, making hardening of the arteries (arteriosclerosis) and clots more common, as well as aggravating platelet problems in women who have inadequate blood volume expansion. Smoking causes hormonal changes by speeding up the metabolism. Nicotine raises serum glucose and free fatty acid levels as well as elevating adrenal hormone levels; the stress hormones in the mother’s and baby’s bloodstream. The nervous system is both stimulated and depressed by nicotine, which can slow the transmission of neurologic signals.
Smoking is associated with decreased fetal weight, and an increased risk of miscarriage and stillbirth. In men it causes the sperm to be abnormally shaped. On the average, babies born to smokers are about half a pound lighter than those born to nonsmokers. From 18 weeks on, fetal head diameter is less than average. The more a woman smokes the greater the reduction in newborn birth weight. However, if she quits by the fourth month the risk of a small-for-dates infant is much reduced. Please note that these studies do not take maternal nutrition into account. When women are truly well nourished, many of these risks are substantially reduced (Brewer, 1983).
The risk of miscarriage, fetal and neonatal death, placental problems such as abruption, previa and bleeding and premature rupture of membranes goes up with the number of cigarettes smoked. For example, miscarriages in women who smoke up to 10 cigarettes daily are 46% more common than in nonsmokers. The risk of fetal death or death in early infancy goes up by 20% for parents that smoke less than a pack per day and by 35% at over a pack a day.
During smoking , blood flow to the placenta is reduced, although the better women eat, the less the baby will suffer (Fox,1991; Brewer,1983). Acute constriction of maternal vessels beneath the placenta lasts up to 15 minutes after a cigarette is extinguished. A larger placenta relative to fetal weight forms when a woman smokes, probably as an adaptation to compensate for fetal hypoxia. However, smokers’ placentas are also lighter in weight and have fewer blood vessels than those of nonsmoking women. Smokers have more mineral deposits in their placentas, giving the surface a grainy texture. This mineralisation causes the placental tissue to be more friable and decreases the amount of nutrient and oxygen exchange that can take place when coupled with inadequate maternal blood volume. Since mineralisation of the placenta generally increases as pregnancy advances and a smoker’s blood volume may not expand as much as a non-smoker’s because of appetite suppression, smokers are at higher risk if they carry their pregnancies past their due date.
Data suggests that maternal smoking during pregnancy may also have long-term effects on the baby’s growth and intellectual development. Small-for-dates infants may have difficulty maintaining body heat and electrolytes immediately after birth, and may have longstanding impairment of growth and intellectual functioning. Newborns of smokers are less responsive to sounds and less easily consoled by soothing sounds. At ages seven and eleven, the children of smoking others showed slight but definite lags in growth as well as poor reading and math test scores. Sudden infant death syndrome is increased as well. Older children living in smoking households are subject to more respiratory problems and infections than those in smoke-free households. Even passive smoke (the presence of smoke in the air being breathed) results in higher levels of nicotine metabolite in a child’s blood. Childhood cancer risk is increased, especially for non-Hodgkin’s lymphoma, acute lymphoblastic leukemia, and Wilm’s tumour. In short, the bad news about smoking, both in and out of pregnancy, just keeps rolling in.

Some ideas on how to stop

Smoking is an addiction and as such, a hard habit to kick. Even though the initial cigarettes that one smokes may make one feel sick, smoking begins to feel pleasurable as these unpleasant symptoms of toxic intake subside. This is due to the release of endorphins, proteins named from a combination of the words “endogenous” (made in your body) and “morphine”. These neurotransmitters are produced in the pleasure centre of the brain in response to recurrent painful or cell damaging stimuli. Cigarette smokers literally get high from their habit. Moreover special times of the day or certain events can become associated with smoking particular cigarettes, which is part of the psychological component of the addiction.
Many methods are used to quit smoking including tapes, programs, hypnosis etc. I say, use anything that works! Here is one plan that can be used in its entirety or in parts to help you to develop a program to quit before or during pregnancy.

Make a decision about when to quit. Set a date. This allows psychological adjustment in preparation for the big day.
Make a 100% commitment to quitting. It is best to commit because you want to do it, not to please a relative or because it’s best for the baby. If you do it for yourself, you won’t project anger to the baby or someone else for putting you through withdrawal. Feeling your feelings and being honest with yourself about why you smoke will help in keeping your commitment.
Make an honest evaluation about how much you smoke, when you smoke and as much as you can get in touch with, why you smoke when you do. When reaching for a cigarette, first, close your eyes, breathe into your chest and body and ask yourself what you are feeling. You should notice any body sensations that arise and ask yourself what they are about. Body sensations are linked to emotions and smoking can effectively distract you from your feelings.
Evaluate your support system, both professional and personal. Do you have a friend who is a former smoker that could support you through the process, such as being available for telephone calls or visits when things get rough?
While some people can quit cold turkey once their mind is made up to do so, many will benefit from a gradual program in which they eliminate ¼ of their cigarettes each week for 4 weeks. This helps to minimize stress and cravings. You should save the elimination of “favourite” smokes for the last week, after you have 3 weeks of success behind you.

The good news is that quitting has an almost immediate beneficial effect on the pregnancy. Within 48 hours after stopping smoking, a mother’s blood carries 8% more oxygen to the baby.

Dietary Supplements                                             

As smoking is eliminated, stored toxins in tissues and cells will begin to pour into the body. Drinking plenty of water will help the body to eliminate them quickly.
It is advisable to eat 2 large and varied servings of fresh vegetables daily. This will replace lost nutrients and add roughage so that the bowels can detoxify at their peak efficiency. Whole grains and legumes (beans, peas etc.) will help replace depleted B vitamins. Supplementation of B and C vitamins is helpful.
Recommended amounts: Vitamin B complex: 50-75mg daily
Vitamin C: 1g daily
Zinc: 50mg daily

Exercise:

Light aerobic exercises such as bicycling, swimming or brisk walking are ideal ways of helping the body mobilize toxins. It also provides the body with a healthier stimulus to produce endorphins.

Replacing the habit:

Since smoking is a way of attempting to nurture the self, quitting often brings up a sense of loss. It may be important for you to substitute the ritual of smoking with an alternative “thing to do” at those times when a cigarette was the most satisfying. Reading a good book, calling a friend, taking a long bath, having a massage now and then, listening to music and allowing yourself to feel your feelings are just a few of the ways that you can reward yourself without having to smoke.

Excerpt from Anne Frye (Holistic Midwifery)