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  • Bryna Sampey, IBCLC

What's in a weight?

Grading on a curve:

When evaluating babies, one of the things we look at is weight gain. This tells quite a bit- namely how well baby’s eating (especially at the breast, where the exact intake is almost impossible to quantify- even with a very specialized scale), what baby’s body is doing with the food they’re taking in, and how quickly baby is growing— It’s quite an important bit of data!

I worry, though, when it’s the only bit of data that gets the spotlight. As a lactation consultant, I know that there are so many nuances that effect infant growth- and specifically weight gain that I often think it must be impossible to suss out true and accurate average for infant weights in the US- and yet, there it is- in every electronic medical records program in every doctors’ office a chart, and a calculation of your baby’s spot on the curve.

That percentile number, it sort of feels like a grade, doesn’t it?

Let's start with the centile numbers: That's the 50th, 75th, 95th percentile number you hear when your baby's weight is charted at the doctor's office. Being in the 50th percentile means that 50% of the babies' whose data was input into that data set are larger than your baby, and 50% are smaller. Being in the 5th means that 95% of babies in that data set are larger than your baby and 5% are smaller- and being in the 95th means that 5% of babies in that data set are larger than your baby, while 95% are smaller. Charts can be narrowed in different ways: weight-for-age, length-and-weight, head circumference, boys' weight for age, girls' weight for age, breastfed growth, mixed-fed growth, etc. Different data sets are available to compare baby to, as well. There are national growth standards, broken out by state and sometimes county- and there are international charts to compare to, as well. The same baby can fall in many different places on a growth chart, depending on the data set!

Every day I talk to parents who worry, worry, worry about their baby’s weigh & growth. Is my baby eating enough? Too much? When we charted his weight the doctor said…

There’s more to the story:

I take a lot of this with a grain of salt- because we look at the whole baby, not just the numbers on a scale. Just some of the things I look at are: baby’s body- for tight muscles, cranial molding, oral function, baby’s reflexes, compare what baby is doing to what they should be doing at that age and stage, hydration, baby’s skin condition, and other factors. I also look at the whole parent- one cannot exist without the other! I check the breastfeeding parent’s milk production, breast tissue, nipples for damage, watch baby’s eating, listen to swallows, breathing, ask about nutrition & bowel movements in both parent and baby…get the picture? It’s a big one! It’s not just about weight gain- though it can be helpful to determine certain things, it can get skewed, too.

For example, we expect babies to gain 15-30g/day for the first 3 months of life. Then it slows to a more measured and coalesced gain- babies go through “growth spurts” and go for periods of time without gaining anything in-between. That 15-30 is a sliding scale of “within normal limits” and it is not a competition where only the babies at the top of the scale are winning! If a baby is doing well and is consistently gaining, say, 20g/day- there isn’t necessarily an indication for supplementation! In fact, including a supplement can sometimes do more harm than good for a baby where nothing is wrong- because we can create problems where there were none.

WHOse chart?

Even when looking at growth curves- we are looking at references from local curves vs national & international standards. From Valerie Natale & Anuradha Rajagopalan’s thorough review in 2014: “The WHO's position is that unconstrained growth of economically advantaged breastfed infants and children does not vary substantially, and that a single set of growth curves can describe a human physiological norm up to age 5. Accordingly, the WHO calculated a set of normative curves from the Multicentre Growth Reference Study (MGRS). Study participants came from single cities in six countries (Brazil, Ghana, India, Norway, Oman and the USA).

The WHO refers to its curves as "growth standards;" Or, "tools that provide a norm or desirable target, involve a value judgement, and describe how children ‘should grow’ in all countries." Standards are different from references, which show how children are actually growing in a given place and time.

The WHO notes that any deviations from its standards should be considered as evidence of ‘abnormal growth’. To date, >100 countries have adopted the MGRS curves...” This means there are multiple different places to check baby’s overall pattern of growth against- and we are not necessarily using all the different data available. If we suspect a problem in baby- are we referencing baby’s growth pattern against local references? International standards? What chart is your doctor or midwife using? It is important to know before doing something like adding a supplement to the parent's own milk, because this can cause more problems than it solves, and end a breastfeeding relationship.

Babies make their own curve:

When using a chart, we should be looking to see if baby has “jumped a line” (which means to change their place in the percentile groups) quickly, or is maintaining their own steady upward curve. A good indicator of appropriate gain is a gentle upward curve that is maintained- meaning baby's on the same or similar line that they were born on- with no plateaus or dips for the first 3 months. A sharp increase or decrease is worth looking into- but without other information, it can be hard to know why it happened. Without extra information, determining a course of action is a bit like flying blind!

Deviations in the same baby’s curve are far more important than not lining up with another baby’s curve. We have to take into account baby’s ethnicity, their parents’ statures, their family growth history... is your head spinning yet?

Why is it important?

So why, when weight is this complicated, do we just look at day-to-day gain, and ignore other signs or health (or trouble) and call it a day? I really don’t know. It is concerning enough for me to write this blog post about! I’m not alone in my concern- the Natale review mentions the WHO’s concern here: “The WHO is correct to be concerned that the potentially smaller size of breastfed infants may lead to erroneous interpretations of growth faltering, followed by premature introduction of supplemental foods. This practice can be deleterious and have significant ill effects on children living in areas where sanitation is poor. However, it is equally important to acknowledge that curves that fit poorly with a population may also lead to errors, such as regarding head growth, FTT or the need for specialist services. These errors can raise barriers to correct diagnosis when a problem exists, create unnecessary stress when one does not and increase strain on overtaxed healthcare systems.”

We expect breastfed babies to grow slower- and though recommendations have been since 2010 to use 2 standard deviations in determining underweight infants (or, infants below the 2nd percentile) the 5th percentile still seems to be the norm. That is to say- if your baby falls at or below the 5% line on the growth chart, you might get a diagnosis of a problem, even though the new recommendations are for 2.3%.

In this vein, I wanted to call attention to babies that might need extra help who don’t get it, thanks to good weight gain and babies who don’t need extra attention and get it anyhow, due to “low” weight gain. There are many examples of babies in both camps in my practice- I asked some of my clients and friends to share some personal stories about weights with you. I encourage you to read through and see what the real cost of “weight-only” assessments can be.

Amelia’s Story:

“We welcomed a stubborn Amelia into this world at 7am on 12/23. I had gone in for a regular visit to my OB and my heart rate was extremely high and I had been experiencing a lot of floaters in my eye that week. It should be noted that at this point I was admitted to the hospital 2 times prior to this appointment, but 2 hours after each admission my contractions magically went away. Due to all this, I was admitted and we talked about starting pit. I was hooked up to IVs for fluid, antibiotic and pit early evening of 12/22. I had over 14 hours of these fluids and such by the time Amelia came. She weighed in at 8lbs 2 oz, and looked like she had been in a UF world title fight, the girl was swollen!! Within a day or two she was down to 7lbs even. This freaked everyone in the hospital out because she lost too much weight. I thought she looked perfect. She had two of the blood tests that required a foot poke at this point and the pediatrician seemed to think everything was ok. We did spend 5 nights and 6 days in the hospital because they considered our c-section to be complicated because Amelia's head was so stuck. (Doctors came in to feel her head because they “hadn't seen one like this in a while" poor girl :( ).

We went to lactation appointments and doctor appointments the day after we were released and it seemed like she was doing well, she was eating and falling asleep when she was done, she had gained weight after feeding. The LC said it wasn’t quite enough, but she wasn’t worried I had a stressful week in the hospital and sometimes it takes time for milk to come in. The pediatrician on the other hand just kept saying how there was a curve and she should be more than 7%. We had an appointment every week for the first week of Amelia's life, she had a total of 4 of the blood tests and was being monitored very closely. My husband and I were getting really nervous because no one talked to us about risks or anything they just kept telling us they were keeping an eye on it.

Finally we went in around 5 weeks, the pediatrician changed his tone and started talking about a condition that would require a minor surgery and we needed to get an ultrasound that day or the next to see if that was it. (I cannot remember what it was called now, but it is when the muscle at the bottom of the stomach was over developed and not letting food he didn’t tell us the name we saw it on the form he sent us home with). He talked about making sure we nursed then fed Amelia everything I pumped after. This was the first time he talked about supplementing at all. He said if I did not get at least 2oz to give her formula up to 2 oz. Though this might be a bit off topic, but he left the room telling us the nurse would come in to tell us when our appointment was and it was for 4 days later...after he made it sound urgent. That night I fed her then pumped 2.5oz and gave all of it to her. She was content (first time in a long time) and slept really well. I felt so guilty that I was starving my baby that I started to panic and the next day I was not getting more than 1 oz when I pumped and she seemed hungry. We gave her a 3 oz bottle and she was fine. We made it to the appointment after trying to figure out how to try and feed her all weekend without much guidance and she ate mostly formula with a little breastmilk. She gained almost 1lb. The tech at the hospital was annoyed we were there because she explained all the symptoms of the condition the pediatrician had suggested Amelia might have and she only had the concern of weight gain. He wanted her to be over the 10th percentile and she wasn't. We ended up changing pediatricians and working with a woman that was more flexible and talked to us more about how to tell if Amelia was healthy. So our experience with the whole bell curve just caused extra stress and I really do see that extra stress as a main motivator for the onset of postpartum anxiety and I do believe that is why I did not nurse as long and my milk never truly came in, I was no stressed out by the doctors and unsure of myself I talked myself out of it.

I am so grateful for the group because it helped calm my anxiety and I only wish I got there sooner to help with my nursing stuff. BUT Amelia is pretty awesome so I am ok with all the choices that were made.”

Sloan’s story:

What %ile did your baby fall on? Sloane was in the 99% at birth and has stayed in the 99 or 98% for her first 5 months.

Did you baby make their own curve? Not yet- we'll see at her 6 month check up, but I'm pretty sure she is still above 95%.

Do you have a story you'd like to share (anonymous or not) about weights and your baby? When Sloane was born, we were able to do skin to skin right away. She nursed on both sides and we had good snuggles. My view was only the birds eye view down her body. I knew she was a big girl, but couldn't really tell. When they weighed her about an hour later, she was 10lb 12oz. I was shocked, and so was the birth team! We were in the hospital and the pediatrician was there. I immediately asked if this put her at higher risk for any conditions or if it was my fault and now she was destined for diabetes! The pediatrician was kind and reassured me that she is just a healthy girl. I appreciated hearing this because I thought that the allopathic opinion of my big girl was going to be that I set her up for future health problems during pregnancy.

Were you ever bullied because of your baby's weight? I haven't been by other moms or friends. My worry is about starting solids. Right now, I feel that I can't over feed her with breast milk and am comfortable with her nursing on demand. We just started giving her solids which is mostly for her to play with and start to taste. I need to read more about feeding toddlers and make sure she stays healthy!

William’s story:

“Where to start. It's been a roller coaster of ups and downs, short term wins and then long term losses. William was born healthy and happy at 6 lbs 6.5 oz. His latch looked fine to the nurses at the hospital, so we proceeded home optimistic about breastfeeding. At our 4 day appointment, William's weight was down 11%, but I didn't think my milk had come in yet, so we were sent home and told to call in the morning with his weight. Low and behold, after he nursed from 9pm to 3am constantly, his weight had gone up! The doctor was happy!

A few days later, in a follow up with our lactation consultant, Bryna, we weighted him again and saw he had flatlined. He was barely getting an ounce from breast-feeding, vs the 2.5-3oz he should be getting. Bryna suspected that he might have a tongue and lip tie, but didn't want to act too soon. The next few weeks are a blur, and honestly it's hard to remember the order of events. I started pumping and feeding him some supplemental milk through a little tube at my nipple. But I was losing my mind, not sleeping and it was crazy making watching that milk creep its way up that little tube, just to go back down again. Will just wasn't able to suck hard enough. At some point we went to Dr. Ghaheri who clipped Will's tongue tie, but wanted to wait on the lip, to Bryna's disappointment. Will still wasn't gaining weight though, so we switched to using the bottle for the supplements to make things a little easier. Introducing the bottle was slow going, but he starting taking it after a few days and gaining weight! Dr was happy again! So we optimistically started to reduce the bottles we were giving him, assuming that he was getting stronger and taking more from the breast, trying to go off his cues. Weight dipped again. So frustrated. My mom came and my husband went back to work, and we got aggressive with the bottle supplementing. 5-7 oz a day in addition to breastfeeding 10x. Pumping 4-5 times a day. I was JUST BARELY making enough milk to cover this (and probably giving him too little so I didn't run out if i'm honest with myself). I felt horrible about the prospect of using formula. He began to gain again, little by little. But not fast enough and Bryna didn't like the look of his latch - he was breastfeeding for 45 minutes and only taking about half of what he needed. And our baby, at 6 weeks, was just back to birth weight at 6lbs 7 oz. People on the street asked me if I'd just left the hospital with my newborn. I was going crazy. At that point Dr Ghaheri agreed to do the lip tie, which immediately improved the latch. Since then, we've had steady weight gain, now up to about 1oz a day. He takes about 8-9 oz in a bottle in addition to breastfeeding, usually 2 of those a day are formula. I often weigh him after feedings to try to estimate the amount that he'll want in a bottle. At 7 weeks I added formula, which was liberating in some ways, sad in others. I still hope to get my supply up to where it needs to be for him. Which is totally fine, but there's just such a stigma attached to formula here, and I just always thought I'd be able to provide for my baby. Hard to face that I can't, even if I might have been able to from the start if his latch was better.

This whole experience has frankly been horrible. I've doubted myself as a mother who can care for her child every day. I've questioned whether I acted fast enough, did enough, understood him enough to make sure he's healthy. My choices and level of concern for my son's health have been questioned by friends and family, potentially damaging relationships long term. I worry that I hurt him and he won't develop correctly because of his slow weight gain. I never imagined spending this much time, effort and tears on his eating and weight. I honestly thought this was the most biological behavior and I'd be thinking about things like sleep. But day and night all we do is talk about his weight, where he is, how much milk he's taken from me, how much from the bottle, how much he's spit up. It's felt never ending.

I am thankful that we've had an amazing team of providers working with us, a lactation consultant and doctor who we totally trust. At his 2 month check in he was 8 lbs 1 oz. Steady growth from about 5 or 6 weeks! But he's still in the 0 percentile for weight. The good news is that height and head size have been progressing according to plan, if not faster! He's in the 25th% for height and similar for head size. Which made me feel much better. I asked the doctor what the goal was. He said, I'd like him to be on the growth chart. It now feels like we have a plan, but the minute you do, he changes on you. His latest is that he won't take a bottle cold (after 4 weeks of doing so). I've just ordered a bottle warmer. Thank god for Amazon.”

Collateral damage:

I’m so, so grateful to the brave mamas that shared their stories- and I wanted to give their words center stage here- sometimes, weight indicates a larger problem, and sometimes, it doesn’t. Sometimes, good weight gain hides an underlying problem, too. When we put on the weight-blinders, we will never know. It behooves us to look at the whole dyad closely, and keep weight were it belongs, as one part of a full assessment. When we enlarge its importance (or minimize it), we do a huge disservice to the families we serve. The fallout is tremendous.

Anxiety over weight begins even in the last few weeks before delivery-

when ultrasounds (which can be off by as much as a pound in either direction) are used to predict birth weight. This leaves many of my clients wringing their hands in fear over their baby's size.

Before or after birth, believing something is wrong with their baby can significantly contribute to a parent's postpartum stress and anxiety, even contribute to ante- or postpartum depression. Supplementation when unnecessary can derail breastfeeding and bring the risks of not breastfeeding along with it— let alone the social stigma of not breastfeeding— and the feelings of guilt and shame that many parents have associated with lack of breastfeeding. Other problems with unnecessary supplementation include sleeplessness on the part of the breastfeeding parent as they’re hooked up to a pump trying to increase a perceived low supply, or get an additional supplement for a baby that doesn’t need it. Over-supplementation in baby can cause over-stretching of the stomach, too, which brings its own host of problems! Did you know that research shows a newborn’s stomach can hold a maximum of 20mL? That’s just a little over half an ounce- not the three I often see suggested in newborn supplementation plans!

The flip side of that coin- not worrying enough- when a baby’s gain is at or above 30mL/day, can contribute to obesity and diabetes (in infants who are bottle feeding), and can lead to missing important signs of trouble- like tongue tie, swallowing difficulties, airway issues, and more. I don’t say this to worry parents. I say this to emphasize that normal or rapid gain (≥30 mL/day) doesn’t mean everything- the same way that normal or slow gain (≤30mL/day) doesn’t mean everything. Like anything else humans do, there is a wide spectrum of normal!

In conclusion:

If presented with issues of your baby’s weight gain, ask questions. There is more to the story! Your care provider may be completely justified in their concern- or they might not be familiar with the variances in growth charts. They might have more resources that you can explore- but you won’t know unless you ask! If you are not finding yourself satisfied, it never, ever hurst to get a second opinion and equip yourself with all the information before making a decision. Thank you, to the mamas for sharing their experiences and thank you, dear reader for sticking with me! Have a weight story of your own? Please share in the comments!


An evaluation of infant growth: the use and interpretation of anthropometry in infants. WHO Working Group on Infant Growth. Bulletin of the World Health Organization. 1995;73(2):165-174.

Natale V, Rajagopalan A. Worldwide variation in human growth and the World Health Organization growth standards: a systematic review. BMJ Open. 2014;4(1):e003735. doi:10.1136/bmjopen-2013-003735.

Grummer-Strawn LM, Reinold C, Krebs NF. Use of World Health Organization and CDC growth charts for children aged 0–59 months in the United States. MMWR Morb Mortal Wkly Rep 2010;55:1–15

Neonatal stomach volume and physiology suggest feeding at 1-h intervals.

Nils J. Bergman

Acta Paediatr. 2013 August; 102(8): 773–777. Published online 2013 June 3. doi: 10.1111/apa.12291

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