How much weight should a newborn gain per week? A guide in grams
The early dip, the weekly gain and what the centile lines in the child health record actually mean.
In short
In the first 3 months a newborn typically gains around 150 to 200 g a week, roughly 500 g to 1 kg a month. Before that, most babies lose up to 7 to 10 percent of their birth weight in the first days and are usually back to birth weight by 10 to 14 days.
- 0 to 3 months: around 150 to 200 g a week.
- 3 to 6 months: around 100 to 150 g a week.
- 6 to 12 months: around 70 to 90 g a week.
- Babies usually double their birth weight by around 4 to 6 months and triple it by around 12 months.
- Weight is plotted on the centile charts in the child health record you are given at birth. The PHN weighs the baby at the home visit and the 3 month check.
A newborn should gain around 150 to 200 g a week in the first 3 months, which works out at roughly 500 g to 1 kg a month. That comes after a normal early dip, so the first fortnight looks different from the weeks that follow.
How much weight does a newborn lose after birth?
Almost every baby loses weight in the first few days. Up to 7 to 10 percent of birth weight is common while feeding gets going and the baby passes the fluid they were born with. A 3.5 kg baby can drop to around 3.2 kg without anything being wrong. The hospital and the PHN keep an eye on this loss, and if it is on the higher side they will look at feeding with you before anything else.
When should a baby be back to birth weight?
Usually by 10 to 14 days. That first climb back is the thing the PHN is checking at the home visit within 72 hours of discharge and on any follow-up weigh-in. If your baby is back to birth weight by two weeks, feeding is almost certainly working, whatever the day to day feeds felt like.
How much should a baby gain each week?
Once they are past birth weight, the pace is fastest early and slows through the year:
| Age | Typical gain per week |
|---|---|
| 0 to 3 months | 150 to 200 g (roughly 500 g to 1 kg a month) |
| 3 to 6 months | 100 to 150 g |
| 6 to 12 months | 70 to 90 g |
Weekly numbers bounce around. A baby can put on 250 g one week and 100 g the next and be perfectly well, which is why the PHN looks at the trend over a few weigh-ins rather than any single one. It also helps to weigh on the same scales, at the same time of day and with a dry nappy, or the noise swamps the signal.
When do babies double their birth weight?
Most babies double their birth weight by around 4 to 6 months and triple it by around 12 months. So a 3.5 kg baby would typically be around 7 kg somewhere between 4 and 6 months and around 10.5 kg near the first birthday. These are averages across many babies, not targets for yours.
What are centile lines?
The child health record you are given at birth has growth charts with curved lines across them. Each line is a centile. If your baby is on the 50th centile, half of babies the same age weigh more and half weigh less. On the 9th centile, 9 in 100 weigh less. Every line is normal. What the PHN cares about is that your baby follows roughly the same line over time, rather than which line it is. A small baby tracking along the 9th centile is doing fine. A baby who started on the 75th and has drifted to the 25th is the one who gets a closer look.
When should I worry about weight gain?
Ask the PHN or GP if:
- Your baby is not back to birth weight by around two weeks.
- Weight gain stalls for more than a week or two.
- Weight crosses down two centile lines on the chart.
- There are fewer than 6 wet nappies a day after the first week, or your baby seems sleepy and hard to wake for feeds.
A baby who is feeding well has around 6 or more wet nappies a day after the first week, so nappies are the quickest daily check between weigh-ins. If you are unsure whether your baby is feeding enough, or how much formula a baby of their weight needs, those guides cover it.
This is a guide, not medical advice. If you are worried, ask your PHN or GP.
How do I know if my baby's weight gain is on track?
Regular weighing at the PHN checks and a look at the centile chart in the child health record. That is the honest answer, and it is what the PHN will do with you. Between visits, Lullagram lets you log each weigh-in and shows the trend against the previous entries, so the PHN conversation starts from real numbers rather than a guess at what the scales said last time. It is free to try on Android, iPhone and web.