Full-term babies, which are babies born at approximately 39 weeks of gestation, typically weigh 6 to 9 pounds at birth. Your newborn, like many healthy newborns, will experience rapid growth spurts at 1, 3 and 6 weeks of age. Your pediatrician will keep a watchful eye on your baby's weight gain to make sure he's growing at a healthy pace, and not too much or too little.
First Things First
Don't be surprised if your newborn loses a few ounces before she starts to gain weight. Babies are born with a little extra fluid, which dissipates in the first week or two of life. Also, intravenous fluids used in labor can transfer to the unborn baby, which is one potential cause for a newborn baby's weight being higher at birth than a few days after birth. It's normal for a formula-fed newborn to briefly lose about 5 percent of his birth weight, while a breastfed infant may temporarily lose from 7 to 10 percent, explains the American Pregnancy Association. It may take mother and baby a little time to adjust to breastfeeding, and the baby may not feed as much during the first few days. A nurse or other trained professional should observe a new mother while she's breastfeeding to ensure that she's using proper breastfeeding technique. Premature or sick newborns may lose more weight after birth, and it may take as long as 3 weeks for the newborn to gain back the weight.
Weight Gain Patterns
Between 1 to 4 months of age, an infant will generally gain 1 1/2 to 2 pounds per month, explains HealthyChildren.org, the website published by the American Academy of Pediatrics. From 4 to 7 months, his weight gain will slow to 1 to 1 1/2 pounds each month. A healthy baby boy will weigh between 14 1⁄2 and 17 1⁄2 pounds at 8 months; infant girls normally weigh about half a pound less than infant boys. By 12 months of age, a baby weighs about three times more than she did at birth. An infant who weighed 7 pounds at birth and 21 pounds at 12 months, gained an average of 1.16 pounds per month.
Around 4 months, breastfed babies will begin to look chubbier than formula-fed babies, according to the AAP. The plump appearance of a breastfed baby gradually fades at around 9 to 12 months, when he may actually become leaner than the average formula-fed baby. The American Pregnancy Association points out that infant growth charts were created with a formula-fed baby in mind, leaving mothers who breastfeed questioning if their baby is normal. The World Health Organization has created updated growth charts, based on breastfed babies but not all pediatricians use them when assessing an infant's growth.
The rapid growth that occurred during the first year of life slows when a baby becomes a toddler. A 3-to-5 pound weight gain is about all you can expect during the entire second year. It will be more than a decade from now when your child reaches puberty, before your child experiences another major growth spurt.
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