Hum. Reprod. Advance Access originally published online on May 26, 2005
Human Reproduction 2005 20(9):2517-2522; doi:10.1093/humrep/dei087
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Smoking habits of parents and male: female ratio in spermatozoa and preimplantation embryos
1 Instituto Valenciano de Infertilidad-Valencia, University of Valencia, 2 Instituto Valenciano de Infertilidad-Barcelona and 3 Hospital Universitario Dr Peset, Valencia, Spain
4 To whom correspondence should be addressed at: Instituto Valenciano de Infertilidad, Plaza de la Policía Local 3, Valencia 46015, Spain. Email: tviloria{at}ivi.es
BACKGROUND: Previous observations have addressed a decreased male:female ratio associated with smoking. Our aim was to assess whether this effect is observed at the spermatozoa or at the early embryo development. METHODS: We retrospectively assessed smoking intake habits of 56 couples included in our preimplantation genetic diagnosis (PGD) program. Three groups were established according to male or female cigarette consumption per day: non-smokers, smokers (1–19 cigarettes per day) and heavy smokers (
20 cigarettes per day). Fluorescence in-situ hybridization (FISH) was performed on ejaculated sperm samples to analyse chromosomes X and Y. On day 3, embryos were also analysed. Additionally, sperm samples from four heavy smoking and four non-smoking donors were prospectively analysed before and after capacitation. RESULTS: FISH on spermatozoa revealed no statistical differences in the Y:X ratio between the three groups. However, in the PGD study, in male heavy smokers, the XY:XX embryo ratio was decreased compared with non-smokers (22:47 versus 80:71; P=0.0057). The smoking condition of the female partner had no significant effect on embryo XY:XX ratio, but for non-smoking females with a heavy smoking partner, the ratio was decreased (P=0.0018) compared with non-smoking males. In heavy smoking donors a decreased of Y:X ratio was observed after swim-up with a statistically significant difference of ratios (P=0.021). CONCLUSIONS: Smoking habits of males do not have an effect on the percentage of X- and Y-bearing spermatozoa on ejaculated samples. However, male heavy smokers produce an increased incidence of female embryos that could be related to an enrichment of X spermatozoa after swim-up in patients with high tobacco consumption.
Key words: cigarette/fluorescence in-situ hybridization/preimplantation genetic diagnosis/sex ratio/sperm