How will my milk change when I am breastfeeding through pregnancy?

Milk supply during pregnancy

Most mothers who are nursing through pregnancy notice a decrease in milk supply by mid-pregnancy, but sometimes as early as the first month. During pregnancy, the mature milk is also making a gradual change to the colostrum which is present at birth. Supply may increase toward the end of pregnancy as colostrum production kicks in.

Why does milk production usually decrease during pregnancy? Progesterone levels gradually rise during pregnancy. One theory for the cause of decreased milk supply during pregnancy (Flower 2003) is that the progesterone makes the alveoli permeable, or “leaky,” so they can’t store milk well. At birth (the delivery of the placenta) progesterone levels drop dramatically, allowing prolactin to take over. Prolactin makes the alveoli impermeable, thus setting the stage for the return of copious milk production.

The production of breastmilk depends upon adequate emptying of the breasts, but the supply and demand regulation of milk supply does not usually hold up when faced with the hormonal changes of pregnancy. The decrease in milk production usually occurs despite continued or increased nursing frequency, although a minority of pregnant mothers do not experience a decrease in milk supply. Obviously if your child does decrease demand, that will further decrease supply.

When your milk supply begins to decrease, your nursling may respond by increasing or decreasing nursing frequency. Your child will most likely make up for decreased milk intake by eating more solids (indeed, increased solid food intake is one way that pregnant moms might track a decrease in milk supply). You can go ahead and encourage increased solid foods – just keep in mind that if your baby is under a year, milk should be his/her primary source of nutrition. As long as your baby is gaining weight adequately and nursing at least 3-4 times a day, he/she is unlikely to need an additional source of milk (see Is my older baby getting enough milk?).

Many moms claim that eating oatmeal once a day helps their milk supply. There are also a number of herbs that can help to increase milk supply, but experts are generally not in agreement when it comes to safe use during pregnancy.

Changes in milk composition

One study compared changes in the milk of two lactating pregnant mothers through the first two months of pregnancy to daily changes in the milk of two women who were gradually weaning (Prosser, Saint & Hartmann 1984). Milk composition and volume changes during pregnancy were similar to those during gradual weaning, but the changes during pregnancy occurred despite continued or increased nursing, rather than in response to a decrease in nursing frequency.


Gradual Weaning

Increased sodium, protein Increased sodium, protein
Decreased glucose, lactose, potassium Decreased glucose, lactose, potassium
Changes were not related to nursing frequency Changes were closely correlated to the decrease in nursing frequency

Source: Prosser CG, Saint L, Hartmann PE. Mammary gland function during gradual weaning and early gestation in women. Aust J Exp Biol Med Sci. 1984 Apr;62 ( Pt 2):215-28.


The changes that accompany the decrease in milk supply would be expected to affect the taste of the milk, and indeed some nursing toddlers mention the change in taste to mom. Once the milk is mostly/fully colostrum, the taste may change again. Some nurslings don’t like the taste change (particularly when combined with the concurrent reduction in milk supply) and may wean as a result. Some love it. Others either don’t seem to notice the change, continue nursing despite the change, or simply don’t mind.

Will I produce colostrum?

Yes. The changeover between mature milk and colostrum production begins, on average, between the 4th and 8th month of pregnancy, but some mothers start producing colostrum somewhat earlier than that. Many mothers who nurse through pregnancy have noted that their milk contains mostly colostrum during the last month before baby is born. You will continue to produce colostrum throughout the latter part of your pregnancy – your older nursling cannot “use it up.”

Colostrum and stool changes in the older nursling

If your older nursling is getting a good quantity of colostrum (either before or after birth), the natural laxative effect of the colostrum may cause him/her to have looser and more frequent stools. The stools should return to normal once your colostrum is completely replaced with mature milk.

Milk changes after birth

At birth, the sudden decrease in progesterone and estrogen levels (and resulting surge in prolactin levels) that occurs with the birth of the placenta causes colostrum production to kick into high gear and signals your milk to “come in.” Once your baby is born, the amount of time you produce colostrum is limited, since your mature milk will begin to come in within a few days.

See also: Does my newborn always need to nurse first?

Will I have enough milk for two?

Both research and anecdotal evidence assure us that a mother breastfeeding two or more children (whether nursing siblings, twins, or more) has the capability to produce large amounts of milk (see Saint, Maggiore & Hartmann 1986). In one study a tandem nursing mother produced a double supply of milk for the entire 7 months that her older child nursed alongside the newborn (see Prosser 1984). As with any nursing relationship, factors like breast reduction surgery or adoption can affect the amount of milk produced, but the only supply concern generally reported by tandem nursing mothers is oversupply, rather than undersupply. See Got Milk? for more information on maintaining and increasing milk supply.

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