Baby weight by stages: growth and reference values

How much weight should your baby gain every month?

During the first few months after your baby is born, one of the things that can worry you most is your baby's weight. It's the reason behind many online searches as well as visits to the paediatrician. That's why our midwives at Happymami have written this post for you, with everything you need to know about your baby's weight by stages.

If you're a mum, you've probably asked yourself the question "how much should my baby weigh?" more than once, because your baby's weight by stages is a topic that comes up again and again. But as common as it is, in most cases your baby's weight progress is normal. We'd also like to tell you that giving an exact figure is very difficult, and that it should always be assessed jointly with a healthcare professional, taking into account other factors such as age, sex, feeding and genetics, among others. How do I know if my baby is getting enough milk?

Newborn under 10 days old

Before we start, and if your baby is less than 7 to 10 days old, you should know that during these days a weight loss of 10% is normal. What does this mean? First of all, that it is completely normal. As an example, a baby who weighed 3,300 grams at birth can lose weight and drop to 3,210 grams over these 10 days, and would still be normal.

In the first month of life

The first month as a mum and dad is usually the acid test. I'd like to go into a little more detail, so I'd like to share with you a table from the World Health Organisation showing the normal weight values for girls and boys by week. In general, the approximate weight gains of babies are:

• 0-6 weeks: 20 g/day
• Under 4 months: 100-200 g/week
• 4-6 months: 80-150 g/week
• 6-12 months: 40-80 g/week

Your baby's weight by stages

Weeks of life	Boys	Girls
0	2.5 – 4.3 kg	2.4 – 4.2 kg
1	2.6 – 4.5 kg	2.5 – 4.4 kg
2	2.8 – 4.9 kg	2.7 – 4.6 kg
3	3.1 – 5.2 kg	2.9 – 5.0 kg
4	3.4 – 5.6 kg	3.1 – 5.3 kg

What's more, if you are breastfeeding, everything is probably going well if the following happens: you feed between 8 and 12 times a day, your baby wets 4 to 5 nappies with urine a day and has several bowel movements a day. And your baby is content and settled after feeds.

From the second to the fourth month of life

At this stage, your baby probably has a more settled feeding pattern and your breastfeeding is well established. During these months, the weight gain is between 100 and 200 grams a week. This gain is a guide: your baby may gain more one week and less the next, but the figures will be around that range.

Between the fifth and sixth month of life

By now, as a mum and dad, you know your baby well, and it's normal to feel more confident about motherhood. The rate of weight gain slows down compared with the previous values, dropping to 500-600 grams a month.

Babies over 6 months

It's time for the introduction of new foods, and the weight gain keeps slowing down, going from 350-400 grams a month at the beginning of the 6 month mark to a gain of 250 to 300 grams a month by the end of the first year of life.

Baby percentiles: what they are and how to read them

A baby percentile shows where your baby's weight (or length, or head circumference) sits compared with 100 healthy babies of the same age and sex. If your baby is on the 50th percentile, half of babies that age weigh less and half weigh more; on the 15th percentile, 15 in 100 weigh less. A percentile is not a score: being higher up is not better than being lower down.

The curves paediatricians use come from the WHO child growth standards (2006), built with healthy, breastfed babies from several countries raised in good conditions. There are separate tables and charts for boys and girls from birth to 5 years: weight-for-age, length-for-age, weight-for-length and head circumference. Percentile charts show five curves: 3, 15, 50, 85 and 97. Your paediatrician may also use other reference charts.

How to read a percentile chart

1. Pick the chart for your baby's sex and the measurement you want (for example, weight-for-age).
2. Find your baby's age on the horizontal axis and their weight on the vertical one.
3. See which curve the point where they meet falls on, or which two curves it sits between.

What matters is their own curve

A single measurement says little. What the paediatrician looks at is the trend over several visits: that your baby roughly follows their own curve, parallel to one of the lines. A baby who stays on the 15th percentile is growing just as well as one on the 85th, because, like adults, each has a build partly determined by their mother's and father's genes. In the first months it is normal for them to move a little before settling into their lane.

When to ask about percentiles

• If over several visits in a row they cross several percentile lines downwards (or upwards).
• If they stop gaining weight or lose weight.
• If their weight falls below the 3rd percentile curve or above the 97th.
• If you also notice any of the signs in the next section.

In those cases, your paediatrician decides whether anything needs doing, taking into account length, feeding and how your baby is.

Reasons to see the paediatrician

As we mentioned earlier, every baby is unique, and whether your baby's growth is optimal should be assessed by their paediatrician, with a comprehensive evaluation of each case. Although the AEPED gives us some recommendations on when to seek advice, and I quote verbatim:

• Prolonged weight loss lasting more than 4 days from birth, or failure to regain birth weight by 14 days of life.
• If the baby is very irritable, very alert or drowsy and unresponsive. (what your baby's crying means)
• Also if they fall asleep after only a few sucks at the breast.
• If the number of soiled nappies (urine and poo) decreases or orange crystals appear.
• If they latch on poorly, with the mouth very closed, far from the breast or sucking very fast. (Breastfeeding guide)

Conclusion on baby weight gain

A child's growth should be monitored by the paediatrician at the consultation once a month or whenever necessary. Weighing your baby more often at home or at the pharmacy can lead to mistakes in managing breastfeeding. You can complete this information with the Newborn Care Guide. We'd also like to remind you that if you need to use a bottle and you want it not to affect your breastfeeding, we have our Happymami, a bottle designed 100% by the mum for her baby. So that there is no difference between breastfeeding or feeding your baby from your Happymami. That way, your baby won't suffer from nipple confusion, protecting your breastfeeding.