Hum. Reprod. Advance Access originally published online on June 24, 2009
Human Reproduction 2009 24(10):2558-2566; doi:10.1093/humrep/dep226
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The number of oogonia and somatic cells in the human female embryo and fetus in relation to whether or not exposed to maternal cigarette smoking
1 Laboratory of Reproductive Biology, The Juliane Marie Centre for Women, Children and Reproduction, University Hospital of Copenhagen, Copenhagen, Denmark 2 Faculty of Health Sciences, Department of Obstetrics and Gynaecology, Frederiksberg Hospital, InnovaCenter, Copenhagen University, Copenhagen, Denmark 3 Research Laboratory for Stereology and Neuroscience, Bispebjerg University Hospital, Copenhagen, Denmark 4 Faculty of Health Sciences, Department of Neuroscience and Pharmacology, University of Copenhagen, Copenhagen, Denmark 5 Faculty of Health Sciences, Department of Obstetrics and Gynaecology, Herlev Hospital, Copenhagen University, Copenhagen, Denmark
6 Correspondence address. Laboratory of Reproductive Biology, Section 5712, Copenhagen University Hospital, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. Tel: +45-35455830; Fax: +45-35455824; E-mail: melissa.lutterodt{at}rh.regionh.dk
BACKGROUND: Prenatal exposure to maternal cigarette smoking or compounds of cigarette smoke is associated with serious reproductive hazards such as apoptotic death of oogonia in murine offspring and decreased fecundability in human offspring. The present study addresses potential effects of in utero exposure to cigarette smoking.
METHODS: Twenty-nine human first-trimester ovaries from legal abortions [aged 38–64 days post-conception (p.c.)] were collected. Mothers filled out a questionnaire about their smoking habits and delivered a urine sample for cotinine analysis. The ovarian cell numbers were estimated using stereological methods.
RESULTS: A non-linear correlation between the numbers of oogonia and somatic cells in relation to age of the embryo/fetus was shown in 28 ovaries, including the first estimates performed in ovaries younger than 47 days p.c. Prenatal exposure to smoke showed a significant decrease in the number of somatic cells (P 
0.01). The number of oogonia was not significantly associated with prenatal exposure to maternal smoking (P 0.09). The ratio between the two cell types decreased considerably from 1:45 to 1:23 from 38 to 46 days p.c. and was not affected by smoking.
CONCLUSIONS: Oogonia proliferate and/or invade the developing ovary at a much faster relative rate than somatic cells. In utero exposure to maternal smoking significantly reduces the number of somatic cells from Days 38 to 64 p.c. Since oocytes cannot survive without being enclosed by somatic cells in a follicle, reduction in the somatic cells number may have long-range consequences on the number of oocytes available in adult life and on the future fertility of female offspring exposed to smoking in utero.
Key words: oogonia/human embryo and fetus/first-trimester pregnancy/cigarette smoking/PAH
Submitted on April 16, 2009; resubmitted on May 18, 2009; accepted on May 29, 2009.