Tobacco smoke contains more than 4000 harmful chemicals, of which a number of them are known carcinogens in humans, whilst others are highly toxic and poisonous.

The chemicals that most affect the foetus and its healthy development are nicotine, tar and carbon monoxide, although arsenic, ammonia, hydrogen cyanide, formaldehyde and creosote are in no way good for the baby to inhale either.

When an expecting mother inhales tobacco smoke from a cigarette, some of the chemicals are exhaled immediately and leave the body, but others stay in the body and make their way into the placenta. The unborn child, as well as inhaling the mainstream smoke that the mother breathes in from the cigarette, which stays in her body, it may also inhale any secondhand smoke that is in the air. This would mean that the growing foetus would be negatively affected by two different types of smoke. Once the baby is born, it would no longer be affected by the mainstream smoke that the mother inhales, however if the mother continues to smoke, the child will suffer the effects of secondhand smoke and become a passive smoker itself.

The unborn child in the womb relies on the mother for its food, nutrients and oxygen in order to develop and grow healthily before the birth. The placenta is the tissue that connects the foetus to its mother and from where it receives all it needs for its correct development whilst it is in the mother's womb.

On smoking several things happen. Firstly, there is a reduced supply of oxygen, due to the increase of nicotine and carbon monoxide in the mother's bloodstream. This means that there is less oxygen available to the baby, as the harmful substances replace it. The baby will begin to move slower after the mother has smoked a cigarette and the baby's heart will have to work faster, as it tries to breathe in more oxygen. Consequently, its breathing and movement will be altered. In other words it will suffer unnecessary stress.

As well as a reduced amount of oxygen, the nicotine constricts the blood vessels in the mother's side of the placenta, thus preventing the blood supply, oxygen and the necessary amount of nutrients and food from reaching the baby, which will result in the slow growth of the foetus.

As a result the foetus will not develop or grow as well as it should and this can lead to the birth of a low-weight baby and all the risks and complications that this could entail. A low-weight baby is more likely to be placed in intensive care once it has been born.

Not only this, once the mother has given birth, she will cut off the supply of nicotine to her child and shortly the baby will begin to suffer the effects of nicotine withdrawal.

Even if the mother does not smoke but the baby is exposed to passive smoking from the father, the growth and development of the foetus can be affected.

Effects on the mother and the pregnancy

Smoking throughout pregnancy does affect both mother and child and can lead to complications that could have been prevented had the mother stopped smoking.

Fortunately some mothers suddenly develop a strong distaste for smoking when they become pregnant and are easily able to give up smoking for the nine-month period or longer.

If you quit smoking within the first 3 months of being pregnant, you are greatly increasing the probability of giving birth to a normal and healthy baby.

Below is a list of possible pregnancy complications that have been associated with women who smoke:

Ectopic pregnancy - this can be life-threatening for the mother and can lead to difficulties in becoming pregnant again. In an ectopic pregnancy, the egg usually becomes implanted in one of the fallopian tubes and begins to grow there. In the majority of cases, this type of pregnancy will never result in the live birth of a child, as there is not enough room for the baby to grow fully, and the cells must be removed as soon as the ectopic pregnancy is diagnosed by either an injection of drugs or by surgery.
Foetal death - this is when the baby is still a foetus (less than 28 weeks) and dies in the uterus. Maternal smoking has been linked to the death of 5 - 10% of all foetal and neonatal deaths.
Stillbirth and death of the baby in the first week - this risk is increased by a third if the mother smokes.
Miscarriage - the risk of suffering a miscarriage is increased by 25% for a smoker.
Placenta previa - the placenta lies extremely low in the uterus and block or covers the opening of the cervix. This can result in a difficult delivery and puts the mother's and baby's life at risk.
Early detachment of the placenta from the wall of the uterus before delivery, which could result in heavy bleeding.
Increase of heart rate and blood pressure in the mother due to the effects of the nicotine.
Blood clots
Vomiting
Vaginal bleeding
Thrush
Urinary tract infections
Premature rupture of the membranes, which may lead to a premature birth as well as infection.
Lack of necessary vitamins and folic acid.
Decreased lung function of the developing baby, caused by the nicotine that crosses the placenta to the foetus and alters the cells of the unborn child's developing lungs.
Premature birth, which could result in a low-weight baby. Full-term babies are healthier and stronger. Going into labour prematurely is twice as common in smokers than it is in non-smokers. The risks are even higher if the mother is still smoking throughout the latter half of her pregnancy.
Respiratory problems in the mother.
Less energy and therefore tiring more easily and less able to cope well with the pregnancy.

Remember, the more cigarettes you smoke throughout your pregnancy, the greater the risks of harm to the foetus, complications with the pregnancy and harm to your health.