Cigarette smoking as a causal effect of infertility

About 30  per cent of  women of reproductive age and 35 per cent of  men in the United States smoke cigarettes.

This is in spite of the  long-standing campaigns to limit tobacco smoking. Several studies have shown a causal link between cigarette smoking and infertility.

A study published by the United States Centers for Disease Control and Prevention showed that while smoking rates among women in the western world have fallen recently, it still remains a major cause of newborn deaths, preterm births and babies with low birth weight.

A systematic review of the scientific literature on the impact of cigarette smoking and  smoke constituents revealed that all stages of reproductive functions are targets of cigarette smoke toxicants.

In the United Kingdom alone, smoking in pregnancy is responsible for about 5,000 miscarriages, 3,000 peri-natal deaths and approximately 2,000 premature births each year.

The WHO states that smoking causes more deaths in one year than all of these combined: deaths due to HIV, illegal drug use, alcohol use, motor vehicle injuries and fire-related incidents.

Smoking causes about 80 per cent of deaths from COPD and 10 per cent of all lung cancers in males and females. More people die from lung cancer each year than from breast cancer.

It cannot be overemphasised that research has established a causal relationship between infertility and smoking. It’s been proved that women who smoke take longer to conceive than women who do not smoke. Some studies found out that tobacco use affects the receptivity of the uterus particularly among heavy smokers.

There’s also a higher incidence of ectopic pregnancies among smokers. Comparatively, low-level smoking, ‘sidestream’ and passive smoking can have detrimental effects on fertility. Recent evidence suggests that smoking affects the success rate of fertility treatment.

Research has also depicted that women undergoing assisted reproductive treatment have a significant negative outcome compared to non – smokers. A study even showed a 50 per cent decline in implantation rate in smokers.

  The impact of tobacco compounds in the process of ovarian follicle maturation is expressed by worse IVF parameters in cycles performed on women with smoking habits. This as well as uterine receptiveness and tubal function are significantly altered by the smoking habit.

Smoking has also been implicated to cause a reduction in the number of germ cells (sperm and egg forming cells) and somatic cells (cells that form the body parts) in utero. It can also affect protamine, a protein essential for sperm production.

Males born to women who smoked in pregnancy are at risk of having small testes, low sperm counts, and low sperm concentration. These men also have a high number of malformed sperm. Nicotine  by-products have been traced in the semen of such men and have been found to reduce sperm motility and their fertilisation potential.

The effects of smoking and alcohol consumption, consequent of our lifestyle and social behavior,  have over the years been proved to have deleterious effects on fertility and have been implicated in early pregnancy losses, preterm births and low birth weight babies.

Women who smoke have been observed  to reach menopause a year or four earlier than non-smokers, shortening their reproductive lifespan. Scientists have said the effects of tobacco on infertility may be ultimately related to oxidative effects.

In females, smoking potentially affects the ovaries adversely. The degree of damage is dependent upon the quantity and length of time a woman smokes. Nicotine and other hazardous substances in cigarette interfere with the body’s ability to create oestrogen, a hormone that regulates follicular growth and ovulation. Smoking interferes with folliculogenesis, embryo transplant, endometrial receptivity, endometrial angiogenesis, uterine blood flow and the uterine endometrium. Smokers are 60 per cent more likely to be infertile than non – smokers.

Smoking decreases the chances of IVF producing a live birth by 34 per cent and increases the risk of an IVF pregnancy miscarrying by 30 per cent. Some damage is irreversible, but stopping smoking can prevent further damage.

In males, oxidative stress occurs in the seminal fluid of smokers. Increased concentrations of cadmium, lead and ROS are significantly higher; and at the same time, concentrations of ascorbic acid and the activity of other components of the antioxidant defence are significantly reduced. Ascorbic acid is the principal extracellular water – soluble antioxidant. Therefore, the scavenging capacity of the antioxidant defence system is severely impaired.

Incidence of impotence is approximately 85 per cent higher in male smokers compared to non- smokers and is a major cause of erectile dysfunction (ED). Smoking causes impotence by encouraging arterial narrowing.

Fathers who smoke heavily (greater than 20 sticks per day) at the time of conception increases the child’s risk of childhood leukaemia and shortens the reproductive life span of their daughters.

Evidence has also suggested that female infertility can be damaged in utero if the woman’s mother was exposed to second hand smoke while pregnant. It has also been found that women exposed to cigarette smoke while undergoing IVF or other assisted reproduction technologies treatment can experience adverse pregnancy outcomes.  More epidemiological research is needed to buttress  these suggestions.

Second-hand tobacco smoke is a known reproductive toxin comprising a mixture of at least 4,000 chemical compounds. Non-smokers who are exposed to second-hand smoke  are at  the risk of difficulty becoming pregnant;  having spontaneous abortion; having babies with congenital malformations or giving birth to still births. Chemicals in tobacco smoke alter endocrine functions which in turn affects the release of pituitary hormones. This endocrine disruption is thought to contribute to adverse outcomes including early menopause.

Smoking can also reduce the chances of a woman becoming pregnant and can affect her baby’s health before (in utero) and after (postpartum). It is also implicated to affect man’s sperm, thereby reducing fertility and increasing the risks of birth defects and miscarriages. This it does by damaging sperm DNA.

Smoking is one of the main causes of infertility. Many men and women of reproductive age continue to smoke with only a small proportion of them considering quitting. Women,  particularly when pregnant,  attempt to quit than at any other times during their lives.  Support should come from the baby’s father, family members and friends as well as the health care system e.g. pregnancy smoking helpline, smoking cessation groups, etc.