Infant weight loss after birth

Health care professionals supporting parents with new babies will often encourage parents to weigh their newborns, naked, with each appointment. There are a few reasons that these regular weight checks are important. While it is important to understand that a baby’s weight is just one element of assessing a baby, it can tell us many things about a baby’s health and how they are adjusting to life outside of the womb.

Most healthy newborns will lose some weight right after birth, this is just excess fluid and is not usually a concern. It can be a concern if a baby either loses more than 10% of their birth weight, or if they don’t regain that weight to be back to birth weight by two weeks.

So what does that mean exactly? Well if your baby is born at 3.50kg, or 3500g, then it will be normal for them to lose up to 350g after birth. This means that their weight should not go below 3.15kg. Also, when weighed, nude, at 2 weeks of age the baby’s weight should be at least 3.50kg.

The most likely reason that babies would either lose more than 10% of their birth weight, or not regain back to their birth weight by two weeks, is feeding challenges. At this point assessment and support by a Lactation Consultant or Child Health Nurse is vital. Feeding challenges in the early weeks is common and often minor changes are all that is needed to get baby feeding well. The very real concern is that if the weight loss is not properly assessed, the baby could start to use more energy than they are gaining through feeding, become lethargic or sleepy, and not be able to grow, this is what people have heard described as failure to thrive.

Newborn babies are supposed to feed and sleep, feed and sleep and wee and poo, but the pattern of how much they are feeding, and how much they sleep can be individual and can depend on mum’s milk supply. Some babies are very chilled and naturally sleepy, even after two weeks of age when most infants start to wake up to the world. Often, the only way to know if a newborn is truly getting enough milk and is sleepy due to a full belly is by regular weight checks. Healthcare providers do see babies who are a month old and parents just think they are a quiet, sleepy baby when in actual fact they are lethargic, and not growing due to poor milk intake.  

Coast Life Child Health service offers infant assessment and feeding support appointments that support the baby to get off to a great start, feeding well and thriving.

Jessica Kumar
Child Health Nurse

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