My newborn lost weight- now what?

I’m certain that the most high-stress period of my postpartum journey was the first two weeks. Life changed in an instant the day our son was born, and the various changes took some major adjustment.

I discussed the challenges of breastfeeding and sleep deprivation in previous posts, and I alluded that I experienced significant anxiety when my son lost weight after his birth.

We know that nearly all babies will lose weight immediately after birth. They’ve been at a 9 month long pool party, so you can imagine they are a bit “water logged” when they arrive. Adding to that, their nutrition (placental blood flow) is suddenly cut off at the time of delivery.

Some babies will lose more weight than others, and that often has to do with two things 1)circumstances surrounding delivery and 2) circumstances surrounding early feeding.

We know that babies born via C-Section have higher birthweights and, as a result, lose more weight- this is due to lack of (please excuse the visual)‘squeezing’ in the birth canal that helps eliminate some extra fluid in vaginal deliveries. Babies born via prolonged labor or inductions (longer time in the hospital on IV fluids) can have similarly elevated birth weights. This means that, because of higher fluid content and resulting higher weight at birth, these babies may lose more weight immediately after birth. Intravenous fluids given during induction or cesarean may also play a role in delayed breastfeeding success, and therefore weight loss, by contributing to swelling and breast engorgement.

We also know that breastfed babies tend to lose more weight after birth than formula fed babies. This is because most mothers do not develop a milk supply until day 3-5 of life (aside from small amounts of early milk, called colostrum) and feeding is almost entirely infant driven and difficult to measure. Conversely, formula fed infants receive calories immediately and the amount of formula received is more in the caregivers control. In fact, many formula fed babies are over-fed in their early days of life- their stomachs are tiny and this is hard for caregivers to fathom!

So, your newborn lost weight? Take a deep breath, this is normal.

Now you might be asking- how much weight is okay to lose? In training, I learned that weight loss of 10% of birthweight or greater should be cause for some intervention (previous studies have shown that weight loss over 10% of birthweight puts baby at risk of dehydration and jaundice). Usually around 8%, my interest was piqued. When I experienced the weight loss (of exactly 8%) with my own son- I started to question where this number came from.

What I discovered was that perhaps the issue of infant weight loss was a bit more nuanced than I previously understood. Kaiser Permanente- a massive health system- conducted large studies of breast and formula fed infants in an effort to understand how much weight loss should be considered “high risk” and potentially warrant intervention. Their study confirmed that infants born vaginally tend to lose less weight than infants born by cesarean. At 48 hours of life, median (middle-of-the-road) weight loss peaked at 7% in vaginally delivered, breastfed infants and 8% in breastfed infants delivered by cesarean (that would be an 8lb baby losing about 11 oz!). For formula fed infants, the peak at 48 hours was just under 3% for vaginally delivered infants and 3-4% in infants born by cesarean. The authors even created this tool that uses data from their studies to help pediatricians determine when to intervene for excessive weight loss.

OK- Why am I telling you this when my intended audience is normal people, not other pediatricians? Because I want to make it very clear to you that your baby will lose weight- it might seem like a lot of weight and it might feel scary- but it should not deter you from your feeding plan of choice. I was SO upset to learn my baby had lost 8% of his birthweight at 48 hours—and now I realize, that’s just over the median for vaginally delivered infants in this massive study, AKA that is completely normal weight loss! For a lot of parents, this period of weight loss can define their feeding journey by detering them from continued breast feeding or making them feel they need to switch formula brands. Please, caregivers, take this information and let it comfort you when your baby inevitably loses some weight in those first days of life.

Sources:

Flaherman VJ, Schaefer EW, Kuzniewicz MW, Li SX, Walsh EM, Paul IM. Early weight loss nomograms for exclusively breastfed newborns. Pediatrics. 2015 Jan;135(1):e16-23. doi: 10.1542/peds.2014-1532. Epub 2014 Dec 1. PMID: 25554815; PMCID: PMC4279066.

Miller JR, Flaherman VJ, Schaefer EW, Kuzniewicz MW, Li SX, Walsh EM, Paul IM. Early weight loss nomograms for formula fed newborns. Hosp Pediatr. 2015 May;5(5):263-8. doi: 10.1542/hpeds.2014-0143. PMID: 25934810.