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Why Do Infants Lose Weight After Birth? Unravelling the Science for Anxious Parents


Are you a new parent? If yes, you've probably spent countless hours swaddling, soothing, and feeding your little one. While all this nurturing has deepened your bond, there might be one thing causing you to worry: your baby's weight loss after birth.


But before anxiety takes over, remember that it's normal for newborns to lose some weight after birth. Understanding this phenomenon can help alleviate your worries and ensure you're providing the right care for your bundle of joy. Here's the science behind why newborns lose weight and what you can do to ensure their healthy development.



The Science Behind the Weight Loss

Firstly, let's emphasize the fact that weight loss in newborns is entirely normal. According to the American Academy of Pediatrics (AAP), most healthy-term newborns lose anywhere between 5% and 7% of their birth weight in the first few days. But why does this happen?


Fluid Loss: Newborns carry extra body fluid. Once they are born and begin to adjust to life outside the womb, they naturally shed this excess water, resulting in weight loss.


Meconium Passage: Meconium is a newborn's first stool, made up of materials the baby ingests in the womb, including amniotic fluid, hair, skin cells, and intestinal secretions. As babies pass meconium during the initial days, they lose some weight.


Caloric Deficit: In the first few days, babies often consume fewer calories than they expend because breastfeeding takes time to establish. This caloric deficit can lead to temporary weight loss.



Your Baby's Weight Gain Journey


Most newborns regain their birth weight by the time they are 10 to 14 days old. However, it's important to monitor their weight and feeding habits to ensure healthy development. Regular paediatrician visits will help track your baby's progress and advise on any necessary interventions. One great way to do this is by using Onoco, where parents can log their baby's weight and observe their child's growth on the percentile lines provided by the World Health Organization (WHO). This visual tool can provide reassurance that your baby is on the right track, even after the initial weight loss.





Alleviating Anxious Parents' Worries

We've heard the stories from many new parents. John and Kate, first-time parents, were gripped with anxiety when they noticed their daughter, Emily, had lost weight in her first week. Despite assurance from their paediatrician and monitoring Emily's weight progress on Onoco, the concern lingered, causing restless nights.


And they're not alone. Laura, a mother of two, recalls the anxiety she felt when her son, Michael, experienced the same. "It's a nerve-wracking experience, especially when you're a first-time parent," she says. "You can't help but worry if your baby is healthy and if you're doing everything right."


These concerns are common and understandable. After all, our instinct as parents is to worry about our children. But understanding the science behind your newborn's initial weight loss can help alleviate these fears.



The key is to ensure your baby is feeding properly and regularly, producing enough wet and dirty diapers and seems generally content between feedings. Any concerns should be discussed with your paediatrician, who will provide guidance based on your baby's individual growth pattern.



Final Thoughts

Remember, every baby is unique, and they don't all grow at the same pace. It's normal for newborns to lose some weight after birth. As long as your baby is steadily gaining weight after the first couple of weeks, feeding well, and producing adequate nappies/diapers, there is usually nothing to worry about.


If you're ever in doubt or feeling anxious, don't hesitate to reach out to your healthcare provider. They can provide reassurance, tips, and resources to ensure you feel confident in your journey as a new parent. Furthermore, using helpful tools like Onoco can provide the peace of mind you need, showcasing the trajectory of your baby's weight gain in relation to WHO percentiles.


American Academy of Pediatrics (2014). Guidelines for Perinatal Care, 8th Edition.

Yasmeen, S., et al. (2013). "Meconium-stained amniotic fluid and infant morbidity in term and near-term infants: a case-control study." Canadian Medical Association Journal.


Dewey, K.G., et al. (2003). "Risk Factors for Suboptimal Infant Breastfeeding Behavior, Delayed Onset of Lactation, and Excess Neonatal Weight Loss." Paediatrics. ↩


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