Effect of smoking on IVF is deceptive

A study has shown that smoking improves the chances of a woman producing healthy-looking eggs for IVF (in vitro fertilisation) by disguising defects which increases the chances of a miscarriage later on. Maria Zenzes of the University of Toronto presented the results of her research into the effects of smoking on a woman's fertilisation rate and embryo quality at the annual meeting of the American Society for Reproductive Medicine.

Her earlier research had suggested that carcinogens from cigarette smoke can result in damaged sperm which affects the quality of resulting embryos. Zenzes Looked at 1682 embryos from 271 women undergoing IVF, assessed them for quality and assessed how much the women smoked by measuring levels of cotinine in the fluid surrounding their eggs. Her surprise results showed that smoking appeared to raise a woman's fertility rate and increase the proportion of good-quality embryos she produced.

Zenzes speculated that benzopyrene, one carcinogen in cigarette smoke which is known to inhibit programmed cell death in lung tumours, may be keeping alive defective cells that would normally die. In IVF treatment, embryos which show signs of programmed cell death are not transferred. Zenzes said that hidden abnormalities in smoking women's embryos could be making it difficult to identify which embryos are suitable for transfer, leading to more miscarriages during any subsequent pregnancy.