A baby’s weight can be a big source of stress for breastfeeding mothers. Is my baby gaining too little or too much? Are they on the right percentile? Am I making enough milk? Often, these concerns stem from parents, and even health care providers, not having a good understanding of what is normal when it comes to babies and weight.

So what is normal? Well, to start with, it is normal for babies to lose some weight after birth. Peak weight loss usually happens on day three (just before mom’s milk “comes in”). Weight loss in hospital is often a big concern, and unfortunately, often a reason for breastfed babies being unnecessarily supplemented with formula. Most hospitals use the measurement of 7% loss from birth weight as an indicator of a problem. The latest research however is giving us new insight into normal newborn weight loss. Dr. Joy Noel-Weiss recently completed a research study looking at newborn weight loss and how that weight loss is affected by IV fluids given to mom during labour. Her findings confirmed what many in the lactation community have thought for some time. IV fluids can artificially inflate a baby’s birth weight. Her study found that IV fluids given to mom during labour and delivery, particularly in the two hours immediately prior to birth, have an impact on how much weight a baby loses after birth. All of that extra fluid has to go somewhere, and some of it goes to baby. After a baby is born and gets rid of the extra fluid, it can look like that baby has lost too much weight. One of the recommendations of the study is that all babies be weighed at 24hrs to allow babies to get rid of any extra fluids they may have in their system, and to use the 24hr weight to calculate weight loss/gain rather than birth weight.

In terms, of weight gain, a healthy term newborn should regain their birth weight by about 7-10 days. A healthy newborn baby who is transferring milk well, is a baby who is growing and gaining weight (after about day 3). If your baby isn’t gaining, or is gaining very slowly, it’s a red flag that something isn’t quite right and breastfeeding needs to be assessed. The first course of action should always be to figure out what is causing the slow weight gain. Whether it’s an issue with mom’s milk production or a problem with baby’s ability to transfer milk effectively, the cause of the problem needs to be determined by someone knowledgeable about breastfeeding. In the first few days in hospital, if your baby is not nursing well and weight gain is a concern, then constant skin-to-skin contact and frequent hand expression and spoon feeding of colostrum are the best approach. If you are being pressured to give formula, you can ask for more time and then get help from an IBCLC.

Once breastfeeding is established, we expect babies to gain at a rate of about 5-7 oz per week (close to an ounce per day), for about the first 3 months. Between months 3-12, weight gain tends to slow down. It is normal for the rate of weight gain to slow down, but it is not normal for weight gain to stop completely or for babies to lose weight. The average breastfed baby doubles their birth weight by about 5-6 months, and at 1 year, they typically weigh 2.5 times their birth weight.

The Centers for Disease Control and Prevention (CDC) and the Canadian Pediatric Society (CPS) both recommend that children’s growth be plotted on the new World Health Organization (WHO) growth charts. The WHO charts, unlike the old CDC charts, are based on the growth of babies under biologically normal conditions (breastfeeding, mothers who don’t smoke etc). When looking at a child’s growth, it is important to be comparing their growth with the biological norm.

For many parents (and health care providers!) growth charts can be a source of great confusion and misunderstanding. When you visit your child’s doctor, their weight is usually plotted on a weight for age growth chart. These charts are used to compare your child to others of the same gender and age. If (for example) your baby’s weight falls on the 25th percentile, it means that statistically speaking, 25% of all babies are that weight or below. Or, to look at it the other way, that 75% of all babies are above that weight. It is very important to understand that the percentile itself is NOT an indicator of health. A baby on the 97th percentile is not healthier than a baby on the 3rd percentile, they just weigh more. Someone has to fall in the 97th percentile, and someone has to fall in the third. What is important is whether or not your child is following their own curve. It is also very important to understand that the 50th percentile does not equal normal or healthiest weight.  The 50th percentile simply means that 50% of all babies are that weight or below. Parents should never be instructed to supplement with formula simply because their breastfed baby is following the 3rd percentile or reduce feedings because their baby is on the 97th percentile. That is NOT how growth charts are meant to be used.

Growth charts are screening tools, not diagnostic tools. This means that if a child is not following the expected pattern according to where they are on the chart, then the doctor needs to look closer to see if something else might be going on. It does not automatically mean that there is a problem.  If a doctor has concerns about a child’s growth then that doctor needs to be looking closely at all aspects of that child’s growth and development. There are several different types of charts available from the World Health Organization, and the weight for length charts or BMI for age charts provide a more accurate picture of an individual child’s growth than the the weight for age ones do.

Weight is only one indicator of growth and should never be looked at in isolation. It is necessary to look at the big picture. The most important thing for parents (and health care providers) to remember is  look at your baby, not just the scale. If your baby is alert and happy, content after feeding, pooping, peeing, meeting developmental milestones, feeling heavier, and outgrowing clothes and diapers, then everything is good (look how many other factors besides weight can tell you that your baby is thriving on your milk!).