Breast Changes in Pregnancy and Lactogenesis

The physiological changes that prepare for breastfeeding

By the term “BREAST” we refer to a complex variety of anatomical structures located bilaterally and

lactogenesis and pregnancy

Lactogenesis and pregnancy: the breast anatomy.

symmetrically on the front of the chest. Very reduced in males, in women assumes a highly specialized organ characteristics. Breast is important for reproductive purposes and for baby nutrition, but also plays a major role in aesthetics standards, eroticism and female sexuality because of values associated with its composite message of sexual identity (it is the most evident sexual character), which transmits to the reproductive capacity of the male partner and the ability to transmit highly erogenous sensations to the brain.

Mammary gland also includes skin, nipple and areola, subcutaneous tissue and fat, connective tissue and muscle fibers. During different age (adolescence, reproductive life, menopause) it undergoes significant changes, but it is during pregnancy that realizing its phylogenetically most important function: the lactation.

These changes are dependent on its ability to be a “hormone sensitive” complex structure and therefore able to adapt and follow the different endocrine conditions that characterize women lives. Mainly, during gestation ovarian (estrogen and progesterone), pituitary hormones (oxytocin and prolactin) and placenta exert control over its development, tropism and lactogenesis.

Among the key moments of change, pregnancy and childbirth are certainly the most significant. In fact, during reproductive events mammary gland plays a key role in the species preservation: the lactation.

Lactation (the ability to produce milk and therefore breastfeeding a newborn) is not a simple biological process: in fact, provides a complex series of changes in mammary gland that begin at pregnancy early stages and last throughout breastfeeding period.

During early stages of pregnancy, mammary gland goes has a great expansion first of lobule-alveolar part (future unit secreting milk) and then of fibrous and adipose tissue support. This happen under a constant and progressive hormonal stimulation by several hormonal substances such as estrogen, progesterone, prolactin, insulin, thyroid hormones, placental hormones, growth factors.  This growth of breast tissue, called “Mammogenesis” is largely completed in the first half of pregnancy and is followed by a second phase of gland preparation called “Lactogenesis.”

Lactogenesis consists of a mammary gland functional differentiation that lead to milk production and sees two main phases: a first phase (or Stage I) in which alveolar cells grow and organize, acquiring specific enzymes for milk production under the stimulus of the fundamental Prolactin protein, and a second phase (or stage II) that begins 2-3 days after birth, in which begins milk production. “Stage I” is therefore a period of preparation and acquisition of a glandular specific competence, but, however, the alveolar cells can not exercise because they inhibited the secretion of Progesterone which high levels will be maintained until childbirth, allowing in the meantime only modest secretory phenomena. At birth, the moment in which production of ovarian and placental  hormones (progesterone in particular) suddenly fall down, inhibitions cease and begin what is called “milk supply”, or “Stage II”, the beginning of milk production.


  • It is possible prepare the way to an adeguate Lactation during pregnancy? Absolutely no. There are no behaviors, substances or creams that may affect the delicate process of mammary gland growth and functional differentiation.
  • A small breasts will have problems with breastfeeding preparation and therefore a Lactogenesis deficit? Absolutely no. Having a breast of modest size does not affect the physiological changes in pregnancy and a normal future breastfeeding.
  • The introflexed nipple requires attention? Yes. In these cases, it is good to perform during pregnancy specific exercises under the guidance of qualified personnel.
  • Some medicines can interfere with Lactogenesis? In pregnancy, is usually paid particular attention to medicines and it is very unlikely that medicines would be taken at a dose and for a duration that would interfere with breast development.
  • Preterm birth is a barrier to breastfeeding? Absolutely no. Early preparation of mammary gland allows breastfeeding even in the event of premature birth. Breast milk is really precious for these newborn.
  • What diseases can result in inadequate breastfeeding preparation? Congenital malformations, severe states of malnutrition, some important endocrine disorders.
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Filiberto Di Prospero
Medical Doctor, Consultant in Gynecology and Obstetrics, Endocrinology and Metabolism. Director of Gynecologic Endocrinology Unit at Civitanova Marche General Hospital (Italy). Private clinics in Civitanova Marche, Rome and Milan.

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