乳房解剖學

妊娠六週時乳房開始變大。剛出生時，乳腺只含有小桿狀末端的始基管，在童年時期生長。在青春期，由於脂肪組織形成和乳導管系統擴大，乳房開始變大。但是，在妊娠期，乳房生長和發育最明顯。

懷孕期間的乳房變化
在泌乳分化期（肺泡上皮細胞分化成泌乳細胞）前半期，乳房導管（乳腺）開始分化，形成小裂片。乳腺組織的生長和發育大約從妊娠期第三周和第四周開始，某些乳導管分化，形成小裂片。導管末端部分增生促使多個腺泡形成（腺泡含有可分泌乳汁的乳細胞）。
 
黃體酮、生長激素以及其它激素等都會影響乳腺發育，使小裂片完全分化。在妊娠期後半期泌乳發育期期間出現初乳時分化最明顯。此時，乳腺富含可以合成乳成分的分化乳細胞，包括蛋白質、乳糖、酪蛋白、α-乳白蛋白和初乳脂肪酸，但只有大約30 ml/天的少量初乳。此後，妊娠後期小裂片增長和肺泡分泌顯著。
 
在整個妊娠期，泌乳組織的增長都很明顯，泌乳組織數量大約是泌乳期乳房脂肪組織的兩倍。這些變化通常會引起乳房和乳頭增大。但是，不同婦女的乳房增大差別很大，有的基本上沒有變化，而有的增大很明顯。多數婦女的乳房在妊娠期第 22 週之前增大，但也有些婦女到了妊娠期後期乳房還明顯增大。然而，乳房增大和產後一個月母乳喂養能力或泌乳沒有任何關係。

斷奶後的乳房變化

寶寶斷奶後，乳腺重新形成以恢復到孕前狀態，為下一次妊娠做好準備。這一過程包括去除泌乳上皮細胞，肺泡上皮凋亡，脂肪細胞產生。

研究摘要

Breast volume and milk production during extended lactation in women （英语）

Quantitative measurements were made of relative breast volume and milk production from 1 month of lactation until 3 months after weaning, and the storage capacity ...

Kent JC, Mitoulas L, Cox DB, Owens RA, Hartmann PE (1999)

Exp Physiol. 84(2):435-47
Breast growth and the urinary excretion of lactose during human pregnancy and early lactation: endocrine relationships （英语）

Breast volume and morphology of eight subjects were measured before conception and at intervals throughout pregnancy until 1 month of lactation. Breast volume before conception ...

Cox DB1, Kent JC, Casey TM, Owens RA, Hartmann PE (1999)

Exp Physiol. 84(2):421-34
 

參考文獻

Geddes, D. 2007, Gross Anatomy of the Lactating Breast. In: Hale, T. & Hartmann, P. (eds.). Textbook of Human Lactation. Amarillo, Texas: Hale Publishing.

Pang, W.W. and Hartmann, P.E. Initiation of human lactation: secretory differentiation and secretory activation. J Mammary Gland Biol Neoplasia 12, 211-221 (2007).

Cowie, A.T., Forsyth, I.A. & Hart, I.C. Hormonal control of lactation. Monogr Endocrinol. 15, I-275 (1980).

Cox, D.B. et al. Breast growth and the urinary excretion of lactose during human pregnancy and early lactation: endocrine relationships. Exp.Physiol 84, 421-434 (1999).

Kulski, J.K. and Hartmann, P.E. Changes in human milk composition during the initiation of lactation. Australian Journal of Experimental Biology and Medical Science 59, 101-114 (1981).

Chapman, D.J. et al. Impact of breastpumping on lactogenesis stage II after cesarean delivery: A randomized clinical trial. Pediatrics 107, E94 (2001).

Kent, J.C. et al. Breast volume and milk production during extended lactation in women. Exp Physiol 84, 435-447 (1999).