Abstract
Purpose
To obtain a precise estimate of ovarian follicle density and variation in the number of follicles at several gestational ages during human fetal development.
Methods
Twelve necropsied ovaries from 9 fetuses (gestational age: 24 to 36 weeks) and 3 neonates (who died within the first hours of life) were studied. Ovaries were fixed with 4 % formaldehyde and embedded in paraffin. Serial, 7 mm thick sections of the ovaries were cut and evaluated at every 50 cuts. Follicles were counted in 10 regions (each measuring 625 μm2) of the ovarian cortex and the number of follicles per mm³ was calculated.
Results
The number of follicles per 0.25 mm² ranged from 10.9 (± 4.8) in a neonate to 34.7 (± 10.6) also in a neonate. Among fetuses, follicle density was lowest at 36 weeks of gestation (11.1 ± 6.2) and highest at 26 weeks (32 ± 8.9). The total number of follicles ranged from 500,000 at the age of 22 weeks to > 1,000,000 at the age of 39 weeks.
Conclusion
Our results show a peak in the number of follicles during intrauterine life at approximately 26 weeks, followed by a rapid reduction in this number before birth, providing a step forward towards the understanding of primordial follicular assembly in humans and, ultimately, the identification of the determinants of reproductive capacity.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Baker TG. A quantitative and citological study of germ cells in human ovaries. Proc R Soc Lond. 1963;158:417–20.
Block E. Quantitative morphological investigations of the follicular system in women; methods of quantitative determinations. Acta Anat. 1951;12:267–70.
Forabosco A, Sforza C, De Pol A, Vizzotto L, Marzona L, Ferrario VF. Morphometric study of the human neonatal ovary. Anat Rec. 1991;231:201–5.
Forabosco A, Sforza C. Establishment of ovarian reserve: a quantitative morphometric study of the developing human ovary. Fertil Steril. 2007;88:675–83.
Godin I, Wylie CC. TGF beta1 inhibits proliferation and has a chemotropic effect on mouse primordial germ cells in culture. Development. 1991;113:1451–7.
Gondos B, Bhiraleus P, Hobel CJ. Ultrastructural observations on germ cells in human fetal ovaries. Am J Obstet Gynecol. 1971;110:644–8.
Gondos B, Westergaard L, Byskov A. Initiation of oogenesis in human fetal ovary: ultrastuctural and squash preparation study. Am J Obstet Gynecol. 1986;155:189–92.
Gougeon A, Chainy GBN. Morphometric studies of small follicles in ovaries of women at different ages. J Reprod Fertil. 1987;81:433–8.
Hilscher W. The genetic control and germ cell kinetics of female and male germ line in mammals including man. Hum Reprod. 1991;6:1416–25.
Kurilo LF. Oogenesis in antenatal development in man. Hum Genet. 1981;57:1–8.
Sforza C, Forabosco A. A morphometric approach to the study of human ovarian organogenesis. Ital J Anat Embryol. 1998;103 Suppl 1:51–62.
Author information
Authors and Affiliations
Corresponding author
Additional information
Capsule
Necropsied ovaries from fetuses and neonates were studied and a peak in the number of follicles was observed at approximately 26 weeks, followed by a rapid reduction in this number before birth.
Rights and permissions
About this article
Cite this article
Geber, S., Megale, R., Vale, F. et al. Variation in ovarian follicle density during human fetal development. J Assist Reprod Genet 29, 969–972 (2012). https://doi.org/10.1007/s10815-012-9810-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10815-012-9810-2