How smoking affects fertility and in vitro fertilization

Clear are the negative effects of classic cigarettes, the use of electronic cigarettes and products Heat-not-Burn (HnB), as well as passive smoking on and the outcome of assisted reproduction programmes. Studies from around the world show that smoking can significantly affect female reproductive potential. “Infertility, i.e. inability to conceive after at least 12 months of regular sexual activity without contraceptive measures, affects about 15% of couples of childbearing age worldwide. The phenomenon is observed in Europe, the US and China and is on the rise in South Asia, the Middle East, and North Africa. It concerns couples wishing to have children and affects the quality of life especially of women who suffer psychological hardship, social stigma, economic pressure, and marital problems. The causes are various, including ovulation disorders, trumpet damage of inflammatory aetiology and endometriosis. Fertility also affects environmental factors, such as air pollution and chemicals that cause endocrine disturbances, as well as lifestyle factors, e.g. obesity and the use of tobacco products” explains the expert in Gynecological Endocrinology, Infertility and Aided Reproduction, Obstetrician Gynecologist Dr. Ioannis Papakonstantinou. Smoking has been shown to cause or contribute to a wide range of human diseases, including reproductive dysfunctions. Each of the 4,000 different chemicals contained in tobacco is toxic to the reproductive system. Most research suggests that current smokers have lower fertility. The use of tobacco products has an impact on steroidogenesis (i.e. the production of androgen, progesterone, estrogen, cortisone and aldosterone) from ovaries and folliclegenesis. It negatively affects trumpet and intrauterine function, as well as embryo growth. Evidence suggests it is associated with delayed conception and early menopause. It is suspected that alkaloids (nicotin), heavy metals (cadmium), polycyclic aromatic hydrocarbons (benzo-α-pyrene), nitrosamines and aromatic amines contained in the cigarette may disrupt reproduction by various mechanisms, including DNA damage. Research revealed that women who smoke more than 10 cigarettes daily for over a decade have lower fertility rates, compared to those they never smoked. The effects of using tobacco products especially around conception and during pregnancy, including decreased fertility, ectopic pregnancy, low birth weight and premature childbirth, are difficult. It has also been found that passive smoking prevents arrest. A recent study found that the risk of infertility was increased by 64% with each cotinin (a nicotine-derived chemical compound) growth in serum over 0,136 ng/mL. Based on their findings, researchers stressed the importance of avoiding passive smoking by women who wish to procreate. However, reduced fertility and increased risk of abortion are also threatened by the daughters of women exposed to cigarette smoke during pregnancy or childhood. “In recent decades socio-economic developments have shifted the decision to acquire offspring to older ages, when women now have reduced ovarian stock and lower quality eggs. Thus couples often put their hopes in assisted reproduction techniques. Any factor that could adversely affect a pregnancy should be thoroughly tested and modified. And smoking is one of them, since it has been shown to undermine efforts to have children. It even has a dose-dependent effect – the more the number of cigarettes smoked daily and the time of exposure to smoke increases the risk of damage to the ovary stock. In women undergoing cycles of in vitro fertilization, active smoking has been associated with significantly lower births of live infants and fewer chances of clinical pregnancy per cycle, higher risk of ectopic pregnancy and higher chances of abortion”, stresses Dr Papakonstantinou. Recently, Italian researchers wanted to assess the impact of smoking classic and electronic cigarettes as well as heat-not burn (HnB) products on infertile women performing in vitro fertilization and in particular on the quality of ova obtained from women performing intracellular sperm infusion cycles (ICSI). This involved 410 women indicted at the Unit of Physiopathic Reproduction and Andrology of Sandro Pertini Hospital, from 2019-2022. They all completed a detailed questionnaire investigating smoking consumption, before starting ovarian stimulation with a competitor protocol, taking the ova and the subsequent ICSI technique. The number of eggs recovered, immature ova and the fertilization rate were investigated and compared between smokers and non-smokers and between cigarette smokers against cigarette smokers and heat-not-burn products (HnB) were compared. It was found that the consumption of tobacco cigarettes decreases the ovarian stock and negatively affects the effects of in vitro fertilization with controlled ovarian stimulation. Although they are still little known about the potential effects of alternative smoking methods (electronic cigarette and HnB products), the results show a negative effect on egg parameters in ICSI cycles. Further clinical studies are of course required, according to researchers. “The maintenance of fertility must be a goal of all women. The adoption of a healthy lifestyle, including the cessation of smoking of all forms and exposure to passive smoking could increase the chances of a successful physical conception or artificial insemination,” concludes Dr Papakonstantinou.