So, since we talked about conventional cow milk a couple of days ago as well as soy and organic milks, I thought we should spare a thought for human-produced milk. I have no firsthand experience with human lactation, so please feel free to jump in with your two cents! Many new mothers will tell you, though, that they did not realize how difficult breastfeeding would be. Babies, unfortunately, don’t just attach themselves naturally to a woman’s breast and easily begin to suckle. It is a skill that must be cultivated. (No wonder wet nurses came to be.)
During a woman’s pregnancy a woman’s breasts become enlarged, to varying degrees, due to a chemical released by the placenta called human placental lactogen (HPL). The first stages of lactation begin during the latter part of a woman’s pregnancy. During this period a woman’s breast begin to produce “first milk” called colostrum that can be yellow in color. Progesterone during this time is too high to allow true milk production.
When the placenta is delivered following birth, the woman’s body experiences a sudden drop in progesterone, HPL, and estrogen. This shift causes the breast tissue to begin to produce real milk. Milk will usually be produced within a day or two of birth, though it is not uncommon for it to take longer. Colostrum production will slowly cease over a two week period as mature breast milk as steadily produced. Colostrum is an important part of breastfeeding, though, because it contains larger amounts of antibodies and white blood cells helping to protect the child from germs and food allergies.
After the breasts become more accustomed to producing milk they begin to function on what I call a “made-to-order” system. A woman’s breasts produce milk as the milk is removed from the breasts (through direct latching, breast pumps, or otherwise.) Breasts will continue making milk so long as it is being removed. The only other reasons that would inhibit continued milk production are maternal endocrine disorders, maternal malnutrition, breast hypoplasia, and in some cases lack of sexual activity, as sexual activity increases milk production.
When actually breastfeeding, the mother may experience milk ejection reflex though it is not unusual to not have this experience. Essentially, the muscles in the breast push out the milk which may result in pain or a tingling sensation. Another cause of pain due to lactation is contraction of the uterus. The same hormone that causes the muscles in the breast to contract and express milk also cause the uterus to contract helping it return to its original size. These contractions may range from mild and menstrual-like to severe and labor-like. I shudder to think what they would feel like following a c-section.
That, in a nutshell, is the basic biology of lactation, though it does not begin to touch on the enormous issue of breastfeeding (perhaps in later entries). But here are a few interesting facts about lactation you might not have known:
*Men can lactate, it’s true! They have mammary glands just like women, and it can result due to a hormone imbalance.
*A woman can lactate without ever having given birth. It is a phenomenon known as galactorrhea and happens either due to a specific hormone imbalance, continued stimulation to the nipples, and in rare cases is caused by prescription drugs.
*New born babies often lactate, colloquially called “witch’s milk,” as a result of the mother’s hormones just before birth. It generally only lasts a few hours.
Questions? Comments? Don’t be shy.