There’s one number most new parents carefully watch after the birth of their child, and that’s their newborn baby’s weight. Too much weight gain or weight loss can easily turn into a world of worry, so “average weight” is a common concern for parents. But what does “average” really mean? And what contributes to normal weight loss and weight gain in newborns? Below we answer those questions, and explain why healthy feedings (and regular poops) can be a sign of healthy weight.

Highlights: On average, full-term newborns weigh 6-9 pounds. This depends on many factors, including gender, genetics, parental variables, and mother’s lifestyle during pregnancy. Most newborns lose a small percentage of body weight in the first few days after birth, as they shed extra body fluid they were born with. After initially losing weight, newborns begin to gain an average of 4-7 ounces each week. The best way to monitor your baby’s weight is by attending all scheduled pediatrician well-visits.

What is the Average Weight of a Newborn?

It’s important to keep in mind that a baby’s birth weight varies depending on factors like race, ethnicity, or gestational age (how much time the baby spends in the womb). On average, babies carried to full-term weigh between 6 and 9 pounds. If your baby was born bigger or smaller than the average, your doctor can explain the best way to monitor your baby’s weight. This could involve extra tests, or more frequent check-ups to make sure there’s no cause for concern.

Factors that Contribute to a Newborn’s Weight

Here are a few key factors that can contribute to a newborn baby’s weight:

• Baby’s Gender: Boys tend to weigh more than girls at birth.
• Mom’s Weight: If mom is considered overweight for her height before and during pregnancy, it’s not unusual to have a heavier newborn. If mom is under the average weight for her height, then it’s possible that her newborn will be smaller than average.
• Genetics: Mom and dad’s past and current weight/health can contribute to their newborn’s weight.
• Lifestyle Throughout Pregnancy: Drinking or smoking throughout pregnancy can cause serious issues with a newborn’s weight/health.
• Mom’s Age: Younger moms, especially those in their teens, tend to have smaller babies.
• Birth Order: Firstborn babies will sometimes weigh less than succeeding children.

Newborn Weight Loss

A few days after birth, newborns typically lose about 5-10% of their body weight. This is simply because babies lose extra body fluid after delivery, which shouldn’t be a cause for concern. Within a week, brand new babies will start packing on those ounces, but it won’t happen right away. Remember that newborns don’t need a lot of food during their first few days of life (when mom’s breastmilk is still developing), so don’t worry if it takes that time to see this lost weight come back.

Newborn Weight Gain

After the initial weight loss, newborns start to gain between 4 -7 ounces a week for about 4-6 months. Keep in mind that formula contains more calories than breastmilk, so formula-fed newborns may gain weight a little more quickly. You also have to consider growth spurts! Newborn babies tend to have growth spurts after weeks 1, 3, and 6, so don’t be surprised if your bundle of joy desires more feedings around this time.

How to Monitor a Newborn’s Weight

If you’re a parent who’s tried gently placing your newborn baby on your bathroom scale, you’re not the first and you certainly won’t be the last! Unfortunately, this won’t give an accurate reading of a baby’s weight because these scales are not sensitive enough to detect ounces. Using the scale at your pediatrician’s office during scheduled well-checks is the most accurate way to measure your baby’s weight.

You can also consider your baby’s elimination as a way of monitoring weight. After the first week, newborns should have at least 5-7 wet diapers a day and 3-4 poops a day (breastfed babies might poop more than formula-fed babies). If your newborn seems satisfied during and after feedings, and appears alert after naps, these are also signs that they’re getting enough breast milk or formula for healthy weight gain.

When to Check in with Your Doctor

If your baby’s weight loss or weight gain doesn’t seem to be caused by the common factors mentioned above, it’s important to check in with your pediatrician. Babies who seem unresponsive after waking up, have trouble latching on to the breast or bottle, or are experiencing unexplained weight loss or gain should be evaluated as soon as possible.

The good news is that pediatrician well-visits are scheduled at frequent intervals after birth, so he or she will be able to keep a close eye on your baby’s weight and help you gauge what’s normal.