Breastfeeding Part I

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Today we start a two part series on breastfeeding with Dr. Erin Cleary, Assistant Professor of Obstetrics and Gynecology and Clinician Educator at the Warren Alpert Brown School of Medicine. She’s also the incoming MFM fellow at the Ohio State University — so look out for her in July, Buckeye listeners!

Also, thank you Dr. Daniel Ginn, our first Patreon sponsor — and apologies for the dad joke with your name!

We start today with a discussion of the anatomy of the breast, and in particular with lactation. At the bottom of this post is a corresponding Netter image to guide your listening.

The physiology of lactation is somewhat confusing, but in bulleted summary:
Lactogenesis I Early in pregnancy, human placental lactogen, prolactin, and chorionic gonadotropin contribute to maturation of the breast tissue to prepare for lactogenesis.

  • In the second trimester, secretory material which resembles colostrum appears in the glands.  A woman who delivers after 16 weeks gestation can be expected to produce colostrum.

  • Differentiated secretory alveolar cells develop at the ends of the mammary ducts under the influence of prolactin.  Progesterone acts to inhibit milk production during pregnancy. This makes sense from a viewpoint of energy expenditure- grow your baby first in utero, then switch to focus on growing it with milk.

Lactogenesis II is the onset of copious milk production at delivery.  In all mammals, it is associated with a drop in progesterone levels; in humans, this occurs during the 1st 4 days postpartum, with “milk coming in” by day 5

  • During the next 10 days, the milk composition changes to mature milk.  Establishing this supply is Lactogenesis III, and is NOT a hormonally-driven process like Lactogenesis I or II. Rather, this is supply/demand-driven with expression of milk

  • When the milk is not removed, the increased pressure lessens capillary blood flow and inhibits the lactation process.  Lack of sucking stimulation means lack of prolactin release from the pituitary.

Next week, we’ll be back again with Dr. Cleary discussing breastfeeding myths and contraindications, so stay tuned!

Netter’s Anatomy. Copyright Elsevier texts.