How Much Breast Milk Does a 3-Week-Old Drink?

Breast milk doesn't come in a container that is neatly marked with measurements, so it's hard to know exactly how much your full-term three-week-old infant is drinking in a feeding session.

This can be a stumper if you need or want to express breast milk so your baby won't miss out on the nutritional benefits when you can't be there to nurse.

However, although every baby is different, each newborn seems to have a pattern of number and frequency of feedings. Combine this knowledge with a little math and some medical findings, and you'll be able to make a rough estimate regarding how much breast milk your three-week-old infant drinks.

Frequent Feedings

Full-term, newborn babies usually nurse eight to 12 times per day during the first month of life, according to KidsHealth, who add that you should feed your newborn "on demand."

Most infants will nurse every one and a half to three hours for the first month, and they should never go more than four hours without feeding during both the daytime and the nighttime.The most important thing is that you feed your baby whenever he is hungry to be sure that he gets enough fuel for the rapid growth of the first month. This can make you feel like your life revolves around feeding your little darling 24/7 -- because it pretty much does. No worries about overfeeding him, though. Breast milk is perfectly designed to move through his digestive system quickly, making frequent hunger normal for your three-week-old baby.

Growing Appetite

High angle view of woman breastfeeding baby

How to Switch Back & Forth From Breastfeeding to Bottle Feeding

Learn More

Your newborn's appetite will grow quickly over the first month and then level out over the next six months or so.

While babies who are younger than one month old generally consume less, full-term babies who are one month old consume between 19 to 30 ounces, or an average of 25 ounces of breast milk per day, advises KellyMom. Babies who are exclusively breastfed will consume more breast milk than will those who receive formula supplements.

Express Delivery

Whatever your personal reasons for wanting or needing to feed your 3-week-old infant bottled breast milk, you can calculate how much milk you will need to express. Divide the average daily intake of a one-month-old baby -- 25 ounces -- by the number of times that your infant nurses daily to get the number of ounces consumed per feeding, explains KellyMom. If your baby is a hungry eater, raise your daily estimate to 30 ounces.

Multiply the per-feeding amount of ounces by the number of bottled feedings you expect to need. For instance, 30 ounces divided by 10 feedings per day equals 3 ounces per feeding.

If that infant is expected to eat four times, multiply 3 ounces by four to find that 12 ounces of breast milk will be needed. Because 3-week-old infants usually eat less than one-month-old babies do, you will probably need less milk -- but it is better to be safe than sorry, and you can always freeze unused fresh milk, or simply leave frozen milk unthawed and ready for the next time.

Storing Breast Milk

High angle view of woman breastfeeding baby

How Much Formula for a 4-Month-Old?

Learn More

If you express more breast milk than you can use immediately, freeze it in plastic bottle-liner bags for later use. Fill each bag with the per-feeding amount to minimize waste, and mark the date and amount on each bag. Doernbecher Children's Hospital advises that you can refrigerate fresh breast milk for up to five days. For long-term storage, freeze the milk in the back of your home freezer for up to three months, or place it in a deep freezer -- with a temperature of -20 degrees Celsius -- for up to 12 months. When you are ready to use the milk, it will thaw in the refrigerator in a few hours, depending on the amount and the thickness of the milk. For faster thawing, place the newly filled plastic bags flat in the freezer so that the milk spreads out, making a thinner layer. You can also speed up the thawing process by placing the bag of frozen milk in a pan of warm water -- but do not microwave or boil the milk, as this destroys the protective antibodies.

You can store the thawed breast milk in the refrigerator for up to 24 hours and throw out any leftover after feeding. Do not refreeze breast milk.

Satisfying Your Baby's Appetite

As a new mom, you will have more peace of mind if you remember that all calculations are just estimates and your baby's appetite will fluctuate just like yours does, explains KellyMom. Flexibility is the name of the game. In general, your baby has a built-in sense of satiation, so you can relax and trust her instincts regarding how much is enough.

As long as she has four to six wet diapers per day, regular bowel movements, and she sleeps well and is gaining weight, she is likely eating enough to satisfy her nutritional needs, according to KidsHealth.

If she does not drink much in a bottled breast-milk feeding, she may be snacking on the bottle, waiting for the bulk of her nutrition to come directly from you. If this is the case, be sure to nurse frequently when you are home.