At birth, a rudimentary system of ducts has formed. Development at this stage is diverse, and can range from simple blunt-end tubular structures to well-developed, branching structures with acinar development.
Howard BA, Gusterson BA. 2000. Human breast development. Journal of Mammary Gland Biology and Neoplasia 5(2):119-137.
At birth, the ductal system opens onto the surface through the breast pit (a depression in the skin’s surface). The underlying mesenchyme proliferates to form an inverted nipple, and the skin surrounding the nipple proliferates to form the areola. Hair can be found at the periphery of the areola. Progesterone receptors first appear in the epithelium of the fetal breast between birth to 2-3 months of life.
Duration: 2 weeks
Howard BA, Gusterson BA. 2000. Human breast development. Journal of Mammary Gland Biology and Neoplasia 5(2):119-137.
Ovary weight is approximately 330 mg. Number of oogonia have been reduced to about 2 million at birth.
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.
Oogenisis: Diplotene stage is completed shortly after birth (chromosomes separate and uncoil slightly, some DNA transcription can occur). Oocytes enter a suspended state and meiosis is arrested until puberty. Antral (Graafian) follicles, with a fully developed oocyte, fluid filled cavity (known as the antrum), multiple layers of granulosa cells, and a thecal layer (outside the basement membrane), can be found.
Duration: 2 weeks
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.
At birth, the mammary gland has secretory activity (possibly due to maternal hormones) which subsides within 3-4 weeks after birth.
Russo J, Russo IH. 2004. Development of the human breast. Maturitas 49(1):2-15.