title: Cigarette smoking during early pregnancy reduces the number of embryonic germ and somatic cells.
abstract: BACKGROUND
  Cigarette smoking during pregnancy is associated with negative reproductive consequences for male fetuses in adult life such as reduced testicular volume and sperm concentration. The present study evaluates the number of germ and somatic cells present in human embryonic first-trimester gonads in relation to maternal smoking.
  
  
  METHODS
  The study includes 24 human first-trimester testes, aged 37-68 days post-conception, obtained from women undergoing legal termination of pregnancy. A questionnaire was used to obtain information about smoking and drinking habits during pregnancy. Validated stereological methods were used to estimate gonadal cell numbers in histological sections. Results were also evaluated in the context of previously published data on ovaries from our laboratory.
  
  
  RESULTS
  A significant reduction in the number of germ cells by 55% [95% confidence interval (CI) 74-21% reduction, P = 0.004] and somatic cells by 37% (95% CI 59-3%, P = 0.023) was observed in testes prenatally exposed to maternal cigarette smoking, compared with unexposed. The effect of maternal smoking was dose-dependent being higher in the heavy smokers and remained consistent after adjusting for possible confounders such as alcohol and coffee consumption (P = 0.002). The number of germ cells in embryonic gonads, irrespective of gender, was also significantly reduced by 41% (95% CI 58-19%, P = 0.001) in exposed versus non-exposed embryonic gonads.
  
  
  CONCLUSIONS
  Prenatal exposure to maternal cigarette smoke reduces the number of germ and somatic cells in embryonic male and female gonads. This effect may have long-term consequences on the future fertility of exposed offspring. These findings may provide one potential cause of the reduced fertility observed during recent years.
authors.affiliation: Laboratory of Reproductive Biology, Section 5712, The Juliane Marie Centre for Women, Children and Reproduction, University Hospital of Copenhagen, University of Copenhagen, Rigshospitalet, Blegdamsvej 9, Copenhagen, Denmark.
authors.forename: L S
authors.initials: LS
authors.lastname: Mamsen
authors.forename: M C
authors.initials: MC
authors.lastname: Lutterodt
authors.forename: E W
authors.initials: EW
authors.lastname: Andersen
authors.forename: S O
authors.initials: SO
authors.lastname: Skouby
authors.forename: K P
authors.initials: KP
authors.lastname: Sørensen
authors.forename: C Yding
authors.initials: CY
authors.lastname: Andersen
authors.forename: A G
authors.initials: AG
authors.lastname: Byskov
mesh_terms: D000328:Adult; D005260:Female; D005854:Germ Cells / Q000166:cytology*; D006801:Humans; D008297:Male; D018811:Maternal Exposure; D010053:Ovary / Q000166:cytology / Q000201:enzymology; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011297:Prenatal Exposure Delayed Effects; D012907:Smoking; D013737:Testis / Q000166:cytology* / Q000196:embryology*