Several studies have linked cigarette smoking with infertility, emphasising a causal association that exists between them.
About 30 per cent of women of reproductive age and 35 per cent of men of reproductive age in the United States smoke cigarette, as do a lot of adolescent and teenage girls despite costly and long-standing campaigns to limit their use.
According to the World Health Organisation, infertility in women has ranked the fifth highest serious global disability among populations under the age of 60.
Infertility is a global factor health issue; causes include male factors, female factors, combined factors and idiopathic (unknown) aetiologies. It is a multidimensional problem with socio-economic, cultural and spiritual implications, and a cause of marital disharmony and distress to couples.
Childbearing and raising children are extremely important events amongst couples, especially those of African descent where it is strongly associated with the ultimate goals of fulfillment, happiness and family completeness. In the United Kingdom, infertility affects about one in every six or seven couples.
Infertility is defined as the inability of a couple to achieve spontaneous conception after trying for at least six months or one year for women over 35 years without using any form of contraception despite adequate (at least two to three times on alternate days) sexual (peni-vaginal) intercourse.
Asides advanced maternal age, STDs, congenital/genetic causes, endocrine causes, chemotherapy, exposure to radiation and other known causes of infertility, lifestyle patterns and environmental pollutants such as cigarette smoking play a crucial causative role in infertility.
A study published by the United States Centre for Disease Control and Prevention showed that while smoking rates among women in the western world have fallen recently, smoking still remains a major cause of newborn deaths, pre-term births and babies with low birth weight. Smoking causes about 500,000 deaths each year in the U.S. – which translates to about one in five deaths.
A 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 UK alone, smoking in pregnancy is responsible for about 5,000 miscarriages, 3,000 perinatal deaths and approximately 2,000 premature births each year. Although the data for Nigeria is not available, considering the fact that we have depleted infrastructure and limited health services, these values may be much higher than reported above.
According to the WHO, 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 Chronic Obstructive Pulmonary Disorder and 10 per cent of all lung cancers in males and females.
It cannot be overemphasised that research has established a causal relationship between infertility and smoking. It has been proved that women who smoke take longer to conceive than women who do not smoke. Some studies found that tobacco use affects the receptivity of the uterus, a higher incidence of ectopic pregnancies, particularly among heavy smokers.
Comparatively, low level smoking, ‘side stream’ and passive smoking (inhaling smoke from other people smoking) can have detrimental effects on fertility.
There are recent evidences which suggest that smoking affects the success rate of fertility treatment. Research has 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. Uterine receptiveness and tubal function are significantly altered by 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, concentration and high abnormalities.
Lifestyle and social behaviour 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.
In men, effects of smoking are evidenced by reduction in sperm production, increase in oxidative stress and DNA damage. Sperms from smokers have decreasing fertilising capacity and embryos have reduced implantation capabilities, hence decrease in implantation rates.