Why Do Babies Lose Weight After Birth

Why Do Babies Lose Weight After Birth

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As soon as your baby enters this world, you and your doctors will keep a close eye on their development and growth. Things like head size, length, and weight are all indicators of a healthy baby. But, we shouldn’t obsess over them.

Yet, many parents worry that their newborn starts losing weight a few days after birth. So, to put your minds at ease, we focus in this post on answering the common question: why do babies lose weight after birth?

Let’s get started.

Why Do Newborn Babies Lose Weight ?


On average, a healthy weight for a newborn at birth is between 5.5 pounds to 9 pounds. Thus, if a baby weighs slightly lighter or heavier, it’s usually nothing to worry about. Still, doctors might pay a bit more extra attention after the delivery to ensure there are no potential problems.

After that, you’ll notice that your baby is losing several grams of their birth weight. Again, this is completely normal and, in fact, expected. Doctors say that nearly all healthy babies lose anywhere between 7% and 10% of their birth weight in that first week.

Unborn babies spend most of their nine months immersed in amniotic fluid. So it’s only natural that their bodies would soak up some of it over the course of that time, hence the extra weight at birth.

To transition to life outside the womb, their lungs, skin, and other organs start to shed this extra fluid, hence the weight loss. The fluids also get released in the form of urine during those first few days after birth.

That’s the drop in weight you see on the baby scales when the doctor weighs your baby during that first check-up after delivery.

Do All Babies Lose Weight After Birth?

It’s true that all babies experience some type of weight loss due to the decrease in fluids. Yet, the exact amount varies from one newborn to another, regardless of whether they’re bottle-fed or breastfed.

That said, however, studies show that breastfeeding tends to play a hand in a newborn’s weight loss compared with babies who are bottle-fed. The early days of feeding contains colostrum, in very small quantities, it is not yet the whitish milk we associate it with.

Why? Well, bottles are easy to prepare in advance. This ensures that your newborn gets their full feeding of between 90 and 120 millilitres at every feeding starting from day one.

As we mentioned earlier, the first milk a baby will get is colostrum, they don’t need much of it since it is so nutrient dense. This will last around 3 days.

To us, three days is nothing, but to a newborn, it can mean losing several more grams off of their birth weight but not missing out on any nutrients.

My Baby Didn’t Lose Weight After Birth, Is This Normal?

Losing weight after birth is a common part of your baby’s adjusting to life outside the womb. Although, some babies don’t lose substantial weight after birth.

They probably only lose a gram or two, which is so little that by the time you get to your post-natal checkup, they’ve already put the weight back on.

As long as your baby is getting their daily feedings and pooping normally (black first, then yellow/brown), it’s nothing to worry about. Plus, losing weight after birth isn’t the only indicator that your baby is healthy.

Other factors come into play, like genetics, as well as the mother’s habits and health conditions during the pregnancy. All these have a small hand in your baby’s overall health and development.

There’s also something known as the APGAR scale, which is basically a list of things that doctors look for, like skin tone, to determine a newborn’s health.

This test is carried out one minute after birth, then again five minutes later. After that, the baby is given a score from 0 – 10, where 10 is a perfect score.

We should mention that few babies get a 10. Anywhere between seven and nine indicates that your baby is in great condition, even if they don’t lose some of their birth weight.

weighing a newborn baby

When Do Babies Start Gaining Weight After The Initial Loss?

A healthy newborn will start to regain weight within the first couple of weeks after birth. Then, during the first 30 days of their lives, almost all newborns will gain an average of about 30 grams each day. You should never panic and forcer your baby to gain weight fast before consulting a medical professional.

You can also expect a growth spurt in weight and height during this period. This is usually when your baby is between seven and 10 days old and between three and six weeks old.

Keep in mind that weight and height go hand in hand. So, when it comes to your newborn’s height, expect to see them grow from two to almost four centimetres during their first month. 


Knowing your baby’s birth weight is important, but it doesn’t indicate whether they’ll be fat or thin, healthy or unhealthy. So, the only thing you have to focus on is providing your newborn with proper nutrition and lots of love!