Colostrum lasts about 2 to 5 days after birth before your body begins transitioning to mature breast milk. If you’re asking about stored colostrum, freshly expressed colostrum stays safe at room temperature for up to 4 hours, in the refrigerator for up to 4 days, and in the freezer for up to 12 months.
How Long Your Body Produces Colostrum
Your breasts start making colostrum during pregnancy, and it’s the only milk your baby receives for the first 2 to 5 days after birth. Around day 3 to 5, you’ll notice your breasts feeling fuller and heavier as your milk “comes in.” This marks the shift to transitional milk, which gradually becomes mature milk over the next week or two. The transition isn’t a hard cutoff. Colostrum blends into transitional milk over several days rather than switching overnight.
The small volume of colostrum is by design. A newborn’s stomach on day one holds only about 5 to 7 milliliters per feeding, roughly 1 to 1.5 teaspoons. Frequent feeding during those first days (8 to 12 times in 24 hours) is normal and helps signal your body to ramp up production.
Why Colostrum Matters So Much
Colostrum is dramatically more concentrated than the milk that follows it. It contains about 42 grams of protein per liter, four to five times the protein in mature breast milk, which drops to around 8 to 12 grams per liter. That protein density delivers protective compounds in a small, manageable volume that matches a newborn’s tiny stomach.
The immune benefits are especially striking. Colostrum carries four to five times the antibodies found in mature milk, particularly a type called secretory IgA that coats the lining of a baby’s gut and respiratory tract, acting as a first barrier against infection. It also contains over 5 grams per liter of lactoferrin, a protein that fights bacteria and helps with iron absorption. Mature milk still contains lactoferrin, but at roughly half the concentration.
Storage Times for Expressed Colostrum
The CDC guidelines for storing breast milk apply to colostrum as well. Here are the limits for freshly expressed colostrum:
- Room temperature (77°F or cooler): up to 4 hours
- Refrigerator (40°F or cooler): up to 4 days
- Freezer (0°F or cooler): up to 12 months, though using it within 6 months is best
The type of freezer doesn’t matter as long as it holds a temperature of 0°F or below. A standard kitchen freezer, a chest freezer, and a deep freezer all work equally well. Store colostrum toward the back of the fridge or freezer, not in the door, where temperatures fluctuate more.
Thawing Frozen Colostrum Safely
Once you move frozen colostrum to the refrigerator to thaw, it needs to be used within 24 hours. If you thaw it at room temperature or warm it under running water, use it within 1 to 2 hours. Thawed colostrum cannot be refrozen. Planning ahead matters here: thaw only the amount you expect to use in a single feeding to avoid waste, especially since colostrum volumes are small to begin with.
Collecting Colostrum Before Birth
Some parents collect colostrum during late pregnancy, a practice called antenatal harvesting. NHS guidelines recommend starting between 36 and 37 weeks of gestation. This is especially common for parents who expect breastfeeding challenges, such as those with diabetes, planned cesarean births, or babies with known health conditions that may require supplemental feeding.
The collection process is simple. You hand-express small amounts into individual syringes, cap each one, label it with the date and time, and store it in the back of the refrigerator for up to 5 days. If you won’t use it within that window, move the syringes to the freezer. When it’s time to bring your stored colostrum to the hospital, pack the frozen syringes in a cool bag with ice packs to keep them from thawing during transport.
Volumes will be tiny, sometimes just a few drops per session, which is completely normal. Using a fresh syringe for each expression keeps everything sanitary and makes it easier to thaw only what you need later.