Newborn weight loss

How much weight will my newborn baby lose?

It’s normal for babies to lose a bit of weight soon after birth, but if they lose too much it may be a sign they are not getting enough milk. Babies reach their lowest weight between two and four days after birth and many babies are back to their birth weight by 14 days. Excess weight loss has been reported as more than 3% of birth weight at 24 hours after birth and more than 7% at three days. If your baby has lost excess weight or shows other signs of not getting enough milk, consult your health-care provider as your baby may be underfed or sick.

A) Newborn weight loss

Nearly all normal babies lose weight after birth. That’s because colostrum is not produced in large amounts and babies are with excess fluid in their bodies and quickly lose it after birth. 

Breastfed newborn babies are at risk of not getting enough colostrum or milk and as a result, losing too much weight after birth. To monitor this, babies are weighed at birth and afterwards.  

Weight loss is just one of four ways of assessing how well a newborn is feeding. Newborn babies who are not taking in enough milk will usually show other signs as well.

B) Reasons for normal newborn weight loss

During the first four days, normal weight loss depends on a number of factors, including:

  • How the baby is fed (by breast or with infant formula)
  • How the baby was delivered (vaginally or by Caesarean section) (Deng 2018)
  • The number of hours since the baby was born
  • How much extra fluid the mother was given during labour (Giudicelli 2020)

When mothers receive a lot of intravenous (IV) fluid during labour, their babies may take up some of it. During the first day after delivery, they eliminate (pee out) this extra fluid. This can exaggerate overall weight loss (Chantry 2011; Noel-Weiss 2011). This is especially common when babies are born by Caesarean section.

In this situation, a baby who is actually getting enough colostrum may be wrongly thought to be underfed. This causes unnecessary worry or in the baby being unnecessarily supplemented with infant formula (Deng 2018).

C) Average newborn weight loss

A small amount of newborn weight loss is normal. Typical maximum weight loss has been reported as 3.8% to 8.6% of birth weight, and the lowest weight is generally between days 2 and 4, after which the baby starts to gain weight as the mother’s milk comes in (DiTomasso 2019; Thulier 2016). 

One U.S. study looked at weight-loss patterns in more than 150,000 babies born at or older than 36 weeks of gestation (Flaherman 2015). Researchers calculated the average weight loss during the first days and weeks following birth, taking into account the method of delivery (vaginal or Caesarean) and whether the baby was breastfed or infant formula-fed.

Table: Average (median) Percent Weight Loss from Birth Weight by Hour and by Delivery Method:


Newborn weight loss (%)

Age (hours)


Caesarean section













They found that by 48 hours after birth, nearly 5% of babies with a vaginal birth and 10% of those delivered by Caesarean section had lost more than 10% of their birth weight. This increased to 25% of babies born by Caesarean section at 72 hours after birth. This difference may be because Caesarean section babies are more likely to be born with excess fluid and to have more difficulty starting to breastfeed.

D) Excess newborn weight loss

These curves are used to assess weight loss of newborn babies.

Some health-care providers use the 10% rule: babies should not lose more than 10% of their birth weight. However, even if babies lose too much weight and are underfed, it may take a few days for them to lose 10%.

The Academy of Breastfeeding Medicine recommends babies with a weight loss of more than 3% of their birth weight at 24 hours after birth or more than 7% at three days be assessed (Boies and Vaucher 2016).

The most sensitive tool is the Newborn Weight Tool (Newt) (PSHCH). It is based on weight-loss patterns inmore than150,000 U.S. babies born at or older than 36 weeks of gestation (Flaherman 2015). The Newt looks a growth chart, but instead of tracking percentiles for weight gain, it monitors percentiles for weight loss. It also separates babies into one of four groups (vaginal or Caesarean birth, breastfed or infant formula-fed) so babies are compared to their peers.

E) Returning to birth weight

Many babies are back to birth weight by 10 to 14 days, and most are back by 21 days (DiTomasso 2019). This is illustrated in the following table.

Table: Percent of Babies Not Back to Birth Weight by Day and Type of Delivery (Paul 2016)

A baby born by Caesarean section has a higher risk of not returning to birth weight by Day 14 (Kelly 2019; Paul 2016). A baby who is not back to birth weight by 14 days or is showing other signs of not getting enough milk at any time should be seen by a health-care provider.

Once babies stop losing weight and start to gain, their weight should follow roughly the same percentile on a growth chart. If they have lost excess weight, they may gain quickly and cross curves upwards.

F) When to supplement

Newborn babies are at risk of not getting enough milk and this can have serious consequences. An underfed baby often shows a number of signs that they are in trouble. One of these signs is excess weight loss.

In general, babies may have lost too much weight if they:

  • Have lost more than 3% of birth weight by 24 hours.
  • Have lost more than 7% of birth weight by 3 days. 
  • Are at or below the 75th percentile curve for weight loss on the Newt nomogram.
  • Are not back at birth weight by Day 14.

These babies need a thorough review of their health and breastfeeding. Babies who are breastfeeding effectively, show all other the signs of taking in enough milk, and are slightly underweight may only need close monitoring until they start to gain. Other babies will continue to lose weight until they start taking in more milk.

Please consult your health-care providers as soon as possible if you have concerns about your baby’s milk intake.


Boies EG, Vaucher YE. ABM Clinical Protocol #10: Breastfeeding the Late Preterm (34-36 6/7 Weeks of Gestation) and Early Term Infants (37-38 6/7 Weeks of Gestation), Second Revision 2016. Breastfeed Med. 2016 Dec;11:494-500
Chantry CJ, Nommsen-Rivers LA, Peerson JM, et al. Excess weight loss in first-born breastfed newborns relates to maternal intrapartum fluid balance. Pediatrics. 2011;127(1):e171–179
Deng X, McLaren M. Using 24-Hour Weight as Reference for Weight Loss Calculation Reduces Supplementation and Promotes Exclusive Breastfeeding in Infants Born by Cesarean Section. Breastfeed Med. 2018 Jan 22
DiTomasso D, Cloud M. Systematic Review of Expected Weight Changes After Birth for Full-Term, Breastfed Newborns. JOGNN 2019;11:11
Flaherman VJ, Schaefer EW, Kuzniewicz MW, et al. Early weight loss nomograms for exclusively breastfed newborns. Pediatrics. 2015 Jan;135(1):e16-23

Giudicelli M, Hassler M, Blanc J, et al. Influence of intrapartum maternal fluids on weight loss in breastfed newborns. J Matern Fetal Neonatal Med. 2020 Feb 20:1-7 

Kelly NM, Keane JV, Gallimore RB, et al. Neonatal weight loss and gain patterns in caesarean section born infants: integrative systematic review. Matern Child Nutr. 2019 Nov 27;e12914
Noel-Weiss J, Woodend AK, Peterson WE, et al. An observational study of associations among maternal fluids during parturition, neonatal output, and breastfed newborn weight loss. Int Breastfeed J. 2011 Aug 15;6:9
Paul LM, Schaefer EW, Miller JR, et al. Weight change nomograms for the first month after birth. Pediatrics. 2016;138(6)
Penn State Health Children’s Hospital (PSHCH). Newborn Weight Tool. Hershey Medical Center [Internet]. Hershey, PA: Penn State Hershey Medical Center; [date unknown] [cited Dec 29, 2019]
Thulier D. Weighing the Facts: A Systematic Review of Expected Patterns of Weight Loss in Full-Term, Breastfed Infants. J Hum Lact. 2016 Feb;32(1):28-34