Smoking and Fertility

Smoking and Female Fertility

Compared with non smokers, both current and past smokers have reduced gonadotropin-stimulated ovarian function. A history of increasing tobacco exposure was associated with decreasing serum oestradiol concentrations, numbers of retrieved oocytes, and numbers of embryos. On average, for every 10 pack-years of cigarette smoking, 2.5 fewer mature oocytes and 2.0 fewer embryos were obtained.

Women who smoked during their treatment cycle had approximately a 50% reduction in implantation rate and ongoing pregnancy rate compared with women who had never smoked. Women who quit smoking before their treatment cycle had the same pregnancy rate as non smokers.

Paternal first-hand smoking often results in maternal second-hand smoke exposure, which can have further detrimental effects on female fertility. One retrospective study of 225 women undergoing IVF/ICSI found that women exposed to second-hand smoke had implantation rates that were comparable to those of women who directly smoked (12.0% vs 12.6%) and were significantly lower than the implantation rates of unexposed women (25.0%). Similarly, women exposed to second-hand smoke experienced a significantly lower pregnancy rate than women not exposed to cigarette smoke (20.0% vs 48.3%).

Smoking and Male Fertility

Smoking has been shown to have a detrimental effect on various parameters of semen analysis. A cross-sectional analysis of 2542 healthy men found that on semen analysis, cigarette smokers had lower semen volumes, sperm counts, and percentage of motile sperm compared to men who did not smoke. Further, it was suggested that the relationship between smoking and sperm concentration was dose-dependent.

Men who smoked > 20 cigarettes per day experienced a 19% reduction in sperm concentration. In another large cohort of 1786 men undergoing infertility workup, smoking was associated with decreases in sperm density (15.3%), total sperm counts (17.5%), and total motile sperm (16.6%) compared with non smokers. Morphology (percent of normal forms) as well as ejaculate volume was slightly affected by smoking.

One meta-analysis included 57 observational studies and > 29000 men. Cigarette smoking had adverse effects on all sperm parameters, including semen volume, sperm density, total sperm counts, and percentage of sperm with progressive motility.

1. Epididymis: The epididymis is the site of spermatozoa maturation where sperm develop their tails. However, the adequate maturation of sperm is known to be inhibited by various factors, including smoking.
2. Varicocele: Varicocele is the abnormal dilation of the pampiniform plexus of the veins near the upper and lateral parts of the scrotum. The combination of smoking and varicocele has been found to be correlated with a 10 times greater incidence of oligozoospermia.
3. Erectile dysfunction: Both first hand and second hand smoking have been conclusively proven to be modifiable risk factors for erectile dysfunction.
4. Hypothalamic-pituitary-gonadal axis: Nicotine can alter the hypothalamic-pituitary axis by stimulating the release of growth hormone, cortisol, vasopressin, and oxytocin, which in turn inhibit luteinizing hormone (LH) and prolactin.
5. Testicular endocrine and spermatogenetic function: Direct toxic testicular damage in smokers may interrupt testicular endocrine and spermatogenetic function.
6. Smoking-induced DNA damage in sperm: Tobacco smoke contains harmful compounds and generates reactive intermediates, such as ROS and reactive nitrogen species, which can induce multiple genetic and epigenetic changes.

Smoking and Fertility Treatment

• Smoking reduces the success of assisted reproduction techniques, such as in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI).
• Couples in which the male partner recently smoked had a significantly lower live birth rate with IVF or ICSI.
• Significant association was identified between recent female smoking and the decreased ability to retrieve eggs during IVF.