Here’s why: Babies lose around 10% of their birth weight soon after being born, so even just a few days after being born (and being weighed for the first time), his weight will be below his centile. This is usually the case for around 2 weeks. Until your little one is back up to the weight he should be (according to the centile graph), he should go no longer than 4 hours between feeds and you should wake him up if necessary – newborns need anything from 8 to 12 feeds a day!
You may also need to wake your newborn from daytime naps if they (luckily enough) tend to exceed 3 hour naps. But once this period is over and your child has regained the lost weight and gained weight appropriately, it is then time for you to look at establishing a better day and night routine to encourage your little one to sleep for longer periods during the night.
But this is not just for the obvious benefits to your child, feeding your little one regularly also helps you to establish your milk supply if breastfeeding. To establish breastfeeding and minimise the risk of breastfeeding complications, feeding at least every 3 hours during the day and every 4 hours during the night for the first 2-3 weeks is the ideal.
If you are bottle feeding you should still wake your newborn for a feed until she is following her centile and always follow the instructions on how much formula milk to give (always check instructions on the packet).