Pregnancy and Smoking

Women and Tobacco

Smoking ages women prematurely. Smoking affects the skin (due to vasoconstriction induced by nicotine), causing reduction in blood circulation and oxygen supply and thus favouring wrinkling and premature aging of the skin. Smoke particles also adhere to the skin, producing a bad odour blocking the pores. Hair becomes fragile because of smoke deposits and reduced irrigation of the scalp. Conjunctivitis is more likely to develop because of smoke-induced eye irritation. Teeth can become discoloured due to nicotine and tar deposits. Smoking also increases the risk of gum decay. Bad breath is the most obvious effect. The voice may also be affected.

Women who smoke may have earlier menopause by one or two years compared to non-smokers. They have more facial wrinkles and may have grey hair earlier. Smoking may also increase the risk for osteoporosis, a major cause for fractures in postmenopausal women.

How does smoking affect the baby?

1. Risk of spontaneous miscarriage in early pregnancy is 2 times higher compared to the non-smokers. This may result partly from an increased number of abnormal embryos, with which smoking is associated.
2. Risk of preterm labour and prematurity of baby.
3. Risk of birth defects. Most studies show a relatively higher risk for babies of smoking mothers.
4. Increased risk of abruptio placentae. This is a serious condition where the placenta separates itself prematurely from the uterus before birth, causing abdominal pain and bleeding from the vagina. This condition can lead to danger and even death for both mother and child.
5. Delayed physical and intellectual development in the child.
6. Adverse effects on maternal health e.g. an increased risk of cancer; gut, heart and lung diseases.
7. Possible risk for Sudden Infant Death Syndrome (SIDS).

How does low birth weight affect the baby?

Infants of smoking mothers weigh on average 300 grams less than those of non-smoking mothers. Low birth weight in babies is not due only to prematurity but also to intrauterine growth retardation (poor growth of the baby in the womb).

A growth-retarded baby is one who is not growing well in the mother's womb because of the lack of nutrients and oxygen. Such a baby faces an increased risk of fetal death in the womb and may require an early or emergency delivery by induction or caesarean section.

The baby also has a higher chance of dying in the early period after birth compared to a normal, healthy baby.

Other problems which a growth-retarded or immature baby may suffer from include low blood sugar, low temperature and aspirating meconium in the womb or when it is born, and respiratory difficulties from immature lungs.

How does smoking affect the baby's growth in the womb?

Smoking reduces the transfer of oxygen and nutrients to the baby while it is in the womb. Low birth weight, one of the effects of smoking, may be due to the following:

1. Nicotine found in tobacco smoke constricts and reduces the placental bed blood vessel flow.
2. Carbon monoxide, also found in tobacco smoke, binds preferentially to fetal haemoglobin excluding oxygen. The higher level of carboxyhaemoglobin (a combination of carbon monoxide and haemoglobin) reduces oxygen supply to fetal tissues.
3. The toxic effect of smoking damages the placenta villi and barrier (the attachment lining between the placenta and the womb), thus reducing the transfer of amino acids and other nutrients to the fetus.

How harmful is secondary or passive smoking?

The effects of passive smoking are difficult to quantify. If a non-smoking woman lives in the atmosphere of her husband's cigarettes smoke, the fetus could receive an indirect effect of the smoke through the mother, although the concentration may be lower than from direct smoking. Thus, it is best for the husband to refrain from smoking in the mother's presence, or to quit the habit. The mother is also advised to keep out of smoke-filled areas.

In the case if a mother who cannot give up smoking totally, how many would be permissible?

There is a graduated fetal response to maternal inhaled smoke. That is, the more cigarettes the mother smokes, the more risks for the fetus. There is no cut off point where smoking can be said to not affect the unborn baby. The best advice is not to smoke at all during pregnancy.