Baby weight

As you navigate life as a new parent, baby’s weight will be something that you’ll probably find yourself thinking about a lot. Just like adults, babies come in all shapes and sizes, and when it comes to the average baby weight, this can vary.

The weight of your baby is a very reliable indicator that your little one is growing happily and healthily. Your baby’s weight can also serve to let you know that something’s not quite right, and that further advice and guidance is needed.

Whether your baby is breastfed or formula-fed it’s important to have all the information you need. Here you’ll find lots of helpful advice and information on the infant's average weight in the UK, how this will be recorded, and how often you should weigh your baby.

During your pregnancy, your midwife will be measuring the size of your baby in centimetres. They do this by measuring from the top of your uterus to the top of your pubic bone with a centimetre tape- this is known as the fundal height measurement¹. All the measurements will be recorded in your maternity notes, to ensure that your baby is growing consistently as they should.

There’s a lot of information out there about the average baby weight, and it can feel pretty daunting. The important thing to remember is that every baby is different, and there are so many different factors that can affect how much your baby should weigh. These include²:

• The status of your health during your pregnancy - including your diet and nutrition.
• Whether they’re male or female (boys tend to be a little heavier and taller than girls³). 
• Genetics.

There’s no way to tell exactly how much your baby will weigh once they’re born, or how their weight gain will progress as they grow. And whilst gaining weight is important, the main thing that your midwife and health visitor will be looking for is that your baby is steadily gaining weight and along their centile line on the baby weight chart.

The following chart for baby boys and baby girls is taken from the World Health Organisation (WHO) website⁷. This is just a guide, and if you’re worried about your baby’s weight, be sure to contact your midwife or doctor.

Here’s a breakdown of average baby weights in the UK in the first year: 

Most babies lose weight in the first few days after they’ve been born - this is completely normal. Those babies who are breastfed can lose somewhere between 5 and 7% of their birth weight, whilst formula-fed babies tend to lose around 3 or 5%⁴.

Within 3 or 4 days, the majority of babies will have stopped losing weight^4. Within around 2-3 weeks, most will have regained their birth weight. Some babies may even weigh more than they did at birth³. Once your baby is around 3 weeks old, it's likely that they’ll be getting the hang of feeding, whether that’s with breast milk or if they’re formula fed.

If your baby loses a lot of weight, or doesn’t regain their birth weight within 3 weeks, your midwife will monitor the situation and provide you with the advice you need around your infant’s weight gain³. If you have any questions, or you need any support with feeding your baby whether they’re breastfed or formula fed, don’t hesitate to speak to your healthcare provider for advice.

After your baby is born, once the midwife has checked that all is well and if you've chosen to do some skin-to-skin contact, one of the first things the midwife will do after is weigh your baby⁵.

In the first two weeks of life, your baby will be weighed again, to ensure that they’re regaining their birth weight. After that, if there are no concerns around your newborn’s weight, they’ll be weighed on average³:

• Once a month up to 6 months of age.
• Once every two months from 6 to 12 months of age.
• Once every three months over the age of 12 months.

Whilst there are many drop-in clinics where you can self-weigh your baby, unless there’s a cause for concern, there’s really no need to do so if it causes unnecessary anxiety. You can always speak to your midwife or health visitor and ask any questions you might have, but rest assured that your midwife will probably only weigh your baby more often if they have concerns about your little one’s development.

As they move through infancy and childhood, your baby’s development, growth and weight will be regularly checked at their health and development reviews. These will be done by a healthcare professional, who will record all the measurements and milestones in your baby’s personal child health record (PCHR). You might have heard other parents refer to this as ‘the red book’. The PCHR contains a baby weight chart, so that you can see how much weight your baby is gaining as they grow.

The PCHR will also contain the results of your baby’s 6–8-week check, which is a thorough physical examination and check of your baby’s development. It’s carried out by a GP and covers everything from the weight and length of the baby to head circumference and the health of your baby’s eyes, hips and heart⁶. 

The weight is recorded on something known as a centile chart, and you’ll find this in your red book. It shows the growth pattern and the average baby weight and height gain of healthy children (you’ll recognise these on the chart as curved lines), and the 50th percentile represents the median average for the population. The same centiles are used whether your baby is breastfed, formula fed, or combination fed, and there’s a different chart for boys and girls³.

If you’re a first-time parent, the centile chart can look a little overwhelming, but your midwife and health visitor will fully explain how it works so that you can fully understand and track your baby’s development.

Whether your baby is big or small, they’re expected to put on weight at a steady pace, staying in the same range shown on the centile chart. If your baby is at the top or bottom end of the chart, this doesn’t mean they’re over or underweight; the baby weight chart is unique to your baby’s development. What matters is that they show steady growth along their particular centile line.

Your baby is likely to experience their most rapid weight gain during the first 6 months of life³. After this time, their weight gain will most likely slow down, particularly when they start to move around more.

Ultimately, how much weight your baby gains is individual to them, so it’s important not to compare your baby’s weight gain with that of others - including siblings. Additionally, your baby may not follow the same centile line all of the time. They may go up or down a centile for any number of reasons, including³:

• Growth spurts.
• Adjusting to weaning and solid foods.
• Illness.
• Increasing level of activity as they grow

If you’ve got any concerns at all, always speak to your healthcare provider for advice and reassurance.

If your baby was born prematurely (before 37 weeks), they’ll follow a different chart. They’ll do this for 2 weeks after their original due date, at which point a correction factor will be applied and the standard charts will be used⁸.

If you have any concerns at all about your baby’s weight and overall development, or you're worried about any health issues, you should always speak to your doctor, midwife or other healthcare professional for advice and guidance.

If your baby is struggling to feed, there are a number of things that you can try in order to make things a little easier. If you’re breastfeeding, you could try:

• Experimenting with different breastfeeding positions.
• Spend plenty of time with your baby skin to skin.
• Feed your baby on demand, as this will help to establish and regulate your milk supply.
• Researching breastfeeding cafes and support groups in your local area.

If your baby is formula fed, some of the things you can try include:

• Following your baby’s hunger cues and feeding on demand.
• Talking to your baby, making eye contact and holding them upright as you feed.
• Give yourself plenty of time so that you and your baby don’t feel rushed.

If you'd like to know more about your little one’s weight or have any questions about baby weight gain, why not give one of our friendly experts a call on 0800 977 8880. Or ask us a question online, instantly, using Live Chat Monday to Friday, 8am - 8pm.