At approximately day 1

Oogonial meiosis detected.

Reference

O’Rahilly R, Muller F. 2001. Human embryology & teratology. Third edition. New York: Wiley-Liss.

At approximately day 1

Oncofetal antigens and steroid receptors expressed.

Reference [PubMed Link]

Gould DA, Moscoso GJ, Young MP, Barton DP. 2000. Human first trimester fetal ovaries express oncofetal antigens and steroid receptors. J Soc Gynecol Investig 7(2):131-138.

At approximately day 1

Fetal ovary capable of synthesizing estradiol.

Duration: 2 weeks

Reference

Sizonenko PC. 1993. Sexual differentiation. In: Bertrand J, Rappaport R, Sizonenko PC, eds. Pediatric Endocrinology. Baltimore, MD: Williams & Wilkins.

At approximately day 1

Wolffian ducts begin to regress.

Duration: 2 weeks

Reference

Sizonenko PC. 1993. Sexual differentiation. In: Bertrand J, Rappaport R, Sizonenko PC, eds. Pediatric Endocrinology. Baltimore, MD: Williams & Wilkins.

At approximately day 1

The epithelium has sunk down into the mesoderm beneath the level of the adjacent ectoderm, and forms a flask-shaped structure. The developing structure is now known as a “nipple.”

Duration: 1 week

Reference [PubMed Link]

Hojo R, Zareba G, Kai JW, Baggs RB, Weiss B. 2006. Sex-specific alterations of cerebral cortical cell size in rats exposed prenatally to dioxin. J Appl Toxicol 26(1):25-34.

At approximately day 1

Mammary tissues are localized as discrete structures formed from a solid bud of cells.

Reference [PubMed Link]

Laurence DJ, Monaghan P, Gusterson, BA. 1991. The development of the normal human breast. Oxford Reviews of Reproductive Biology 13:149-174.

At approximately day 1

Steroidogenic ability of early fetal ovaries is possibly due to interstitial cells which differentiate in the medulla and do not seem to be associated with thecal cells.

Duration: 10 weeks

Reference [PubMed Link]

Rabinovici J, Jaffe RB. 1990. Development and regulation of growth and differentiated function in human and subhumand primate fetal gonads. Endocrine Reviews 11(4):532-557.