Baby development

What you need to know about baby weight gain

Concerned that your baby is not gaining weight at a normal rate? Here's what to expect in the first year and what to do if your baby isn't gaining.

By Teresa Pitman
What you need to know about baby weight gain

Photo: iStockPhoto

Eileen Rainey’s second baby, Mckenzie, was a slow-gaining baby right from the start. “She weighed seven pounds, four ounces at birth,” Rainey recalls, “but was very jaundiced and didn’t get back to her birth weight until she was 3½ weeks old. Then she seemed to start gaining faster.”

At four months, though, her rate of weight gain slowed down again. “Between four months and six months, she only gained nine ounces,” says Rainey. “On the other hand, she’d been sick not long before we went to the doctor, and I think that affected her weight.” But her doctor was concerned, and referred her to a paediatrician.

In recent years, our understanding of normal baby weight gain has improved. Valerie Marchand, a Montreal paediatric gastroenterologist and chair of the Canadian Paediatric Society’s Nutrition and Gastroenterology Committee, was part of a group that recommended the use of new growth charts developed by the World Health Organization (WHO). While the previous baby weight gain charts, used to mark down and follow a baby’s growth patterns, were based on formula-fed babies, these new ones were based on breastfed babies who started solids around the middle of the first year.

“The biggest difference between the new charts and the old charts is that breastfed babies grow more quickly in the first four to six months, and then slow down, while formula-fed babies grow more slowly at first and then gain weight faster,” Marchand explains. “So on the old charts, it could look as though a breastfed baby’s weight was faltering. Most paediatricians knew that this was OK, but a lot of parents would worry, and some would wean or add formula.” With the new charts, parents will see that their breastfed baby is gaining appropriately.


What’s normal weight gain for breastfed babies?

These are average expectations for weight gain of breastfed babies:

• In the first few days after birth, babies normally lose weight, then get back to their birth weight by about 10 days. If that’s not the case, says Marchand, the baby and how she is feeding should be assessed by a doctor. • In the first three months, a baby should gain, on average, 140 to 210 grams (five to 7½ ounces) per week. Toronto breastfeeding expert and paediatrician Jack Newman points out that these averages can be misleading. “A baby who is following the 95th percentile on the growth chart will be gaining significantly more. A baby following the third percentile gains significantly less than that. That’s one reason growth curves are a better way to judge how the baby is growing.” • Between three and six months of age, the average rate of baby weight gain slows down to between 105 and 147 grams (four to five ounces) per week. • Between six and 12 months, the average growth rate is 70 to 91 grams (2½ to three ounces) per week. • On average, babies double their birth weight by four or five months, and triple it by a year.

Marchand adds that parents should be aware that a baby’s birth weight depends more on the mother’s diet and health during pregnancy, than on genetics. For example, a mother with gestational diabetes is likely to have a larger-than-average baby, even though the baby’s genetics may actually point toward a smaller size in adulthood. Other babies may be born smaller than average, but be genetically destined to become tall adults. “So some babies need to gain weight quickly to catch up, while others need to ‘catch down,’” Marchand says.

When should you be concerned about your baby's weight?


While slow-gaining babies tend to get the most attention, there are new concerns about babies who gain quickly, especially since the introduction of the WHO charts. “You need to look at height as well as weight,” says Marchand. “A baby who is on the 50th percentile for weight but only the fifth percentile for height may be overweight. A baby on the 95th percentile for both weight and height is probably just fine.”

Rapid baby weight gain is more likely to be a problem for infants who are fed formula, and Marchand comments that sometimes a baby will be drinking 1.7 litres (60 ounces) of formula in a day and growing very quickly. “This needs to be looked at,” she says. “The parents may be misinterpreting the baby’s cues.”

Weight gain is less of a concern for breastfed babies, says Newman. Because breastfeeding babies stop when they’re done (not when the bottle is empty), they are more able to self-regulate their intake. “I wouldn’t worry about rapid growth in a breastfed baby who is content and healthy.”

Newman adds that while tracking baby’s weight gain is a useful tool, it needs to be used wisely. “We are fascinated by numbers, but they are only part of the story. Scales can be wrong, and you can’t reliably compare two different scales (such as the one in the hospital and the one in the doctor’s office). Mistakes in weighing often occur. Observing the baby — especially observing the baby at the breast — tells much more.”

What to do when your baby is not gaining weight

Rebecca Serroul’s son, Sebastian, was born weighing nine pounds, three ounces, but gained slowly and weighed just 18 pounds at a year. His rate of weight gain concerned Serroul’s doctor from around six weeks, but Serroul wanted to continue to breastfeed exclusively until Sebastian seemed ready for solid foods.


Paediatrician and breastfeeding expert Jack Newman says the first step is often to improve the way the baby latches on to the breast. “It’s important that the mother know when the baby is getting milk rather than just ‘nibbling’ at the breast. When the baby is not drinking much, using compression can help,” he adds. Breast compression means squeezing your breast while the baby is sucking, but not drinking — like expressing milk into the baby’s mouth. If the baby’s weight gain has slowed or even stopped, the mother’s milk supply may have decreased, and this needs to be investigated by someone with breastfeeding expertise. More information on possible causes — including videos showing how to latch a baby and how to know when baby is drinking — are on Newman’s website at

Serroul sought help to see if her milk production or her son’s latch could be improved, but found his weight gain stayed about the same. She says plotting Sebastian’s weight on the World Health Organization charts (rather than the older charts her physician was using) reassured her about his growth rate, and since he was content and active, she felt confident in continuing to breastfeed him.

This article was originally published on Jan 09, 2017

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