What to Expect from a 3-Week-Old Baby

Although the behavior of a 3-week-old can seem confusing, it is actually highly organized and complex. Newborns engage in a complex array of behaviors designed to keep them safe, bond with their caregivers, and ensure that their physical and emotional needs are met. Although the few weeks after birth can be exhausting for parents, babies are learning and developing rapidly at that time.


At three weeks, most of a baby's movements are reflex-oriented. Newborns instinctively suck anything placed in their mouth, grab anything placed in their palm and root when the side of the cheek is stroked. Some reflexes are deceivingly complex and may lead parents to conclude that their baby is capable of complex motor skills. However, reflexes are processed through the spinal cord and not the brain, so your baby is not actively thinking about her reflexes.


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At three weeks, many mothers are still struggling with breast-feeding and may suffer from mastitis and cracked nipples. Breast-fed babies tend to weigh slightly less than formula-fed babies, and your baby may not have regained the weight she lost after birth yet. At 3 weeks, most babies eat about 3 oz. of breast milk or formula with each feeding. Your baby may not have yet established a feeding schedule, so feed her whenever she appears to be hungry. This will probably average out to be every 1.5 to two hours.


Newborns spend most of their time sleeping. Expect your child to sleep anywhere from 16 to 20 hours each day. She may sleep less if she has colic. Most babies establish a regular sleeping schedule around six months, so parents of newborns often experience sleepless nights. Your baby will probably wake up every time she is hungry. Many parents of newborns find that keeping their baby in their room makes feeding easier and less stressful.


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Three-week-old babies tend to cry very frequently. It is their sole means of communication, and some babies may appear to cry for no reason. The crying eases up over the course of several months, and by 6 months old, your baby will be crying much less frequently.


Your 3-week-old is already learning at an astounding rate. Developmental psychologist Robin Harwood reports that babies may remember stimuli to which they were exposed as newborns, and that these stimuli may affect neural pathways. Read to your child frequently, and practice talking to her. Babies whose parents read and talk to them read and speak earlier than other children.