Birth to 4 months - What to Expect!

Created: December 12, 2014. - Reviewed: November 27, 2015.

At no time in your baby's life will he go through such rapid change as he does in the first 4 months of life.

Birth to 4 months - What to Expect!
Rowena Bennett

Rowena Bennett

  • Registered Nurse
  • Registered Midwife
  • Child Health Nurse
  • Mental Health Nurse

Rowena over 20 years experience assisting parents to resolve well baby care problems.


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Sesory development


  • At birth your baby's vision is blurry.
  • At 1 month, a baby can only see clearly within 12 inches of his face. His distance vision will increase to several feet or more by the time he is 4 months old. 


  • Your baby has an acute sense of hearing.
  • Young babies respond more consistently to a high pitched voice (female or child) rather than a low one (male). 
  • Newborn are soothed by rhythmic sounds such as a lullaby or heartbeat.

You can tell whether your baby can hear by the following...

  • Sudden loud noises should stir or wake your sleeping baby or startle your baby when he's awake.
  • You may notice an increase or decrease in sucking behaviour in response to sound.
  • He quiets to the sound of a familiar voice.

Speech and language

A newborn's only way to communicate his needs is to cry. His cry will be loud and intense. Later his cry will change in tone and intensity and become different and more specific to identify what he needs or wants. As he matures he learns to communicate in other ways besides crying. He learns to whimper, squeal and coo. At around 3 months he starts to babble, imitate some sounds and laugh.


Birth to 4 months is a period of rapid growth.


  • Average weight at birth is 7½lb (3.4kg). 95% of newborn's birth weight will range between 5½ lb and 10lb (2.5kg and 4.5kg).
  • Almost all babies will lose weight soon after birth, as they are learning to adjust to feeding. A loss of 5-9% of birth weight is common. Most babies will have regained this weight by the time they are 2 weeks old.
  • After the first 2 weeks, average weekly weight gain* is 5 to 8 ounces (150-220gms).
  • Average monthly gain is 1lb 9oz to 2lb (0.7 to 0.9kg).
  • By the age of 4 months an average baby will weigh approx double his birth weight.
  • At 4 months average weight for girls is 13lb 4oz (6.0kg) and for boys is 12lb 13oz (6.5kg).

*Fluctuations can occur if you weigh your baby weekly. Many false alarms can cause parents unnecessary concern. (See When your baby's weight gains decline for more information).


  • Average length at birth is 20½ inches (52cm). 95% of newborns length will range between 18 inches and 23 inches (48cm to 58cm).
  • Monthly increase in body length ranges between 1 inch to 1¾ inches (2.2cm to 4cm).

Head size

  • Average head circumference at birth is 14 inches (34.5cm). 95% of newborns' head circumference will range between 13 and 14¼ inches (32.5cm to 36.5cm).
  • By 3 months your baby's head would have grown approx 1½ to 2 inches (4 to 5cm) in circumference.

Physical achievements

At birth to 1 month your baby can...

At 1 month

  • listen to your voice
  • looks up and to the side
  • tries to watch and follow with his eyes
  • holds things placed in his hand
  • holds his head up briefly when supported
  • raises his head a little off the floor or bed, when lying on his stomach
  • begins to make little sounds

At 2 months

  • listens to musical sounds
  • follows movement and people with his eyes
  • can focus on his hand
  • can reach and hit nearby objects
  • learns to smile
  • holds his head up, bobbing, when held in a sitting position
  • makes cooing and gurgling sounds

At 3 months

  • develops stronger arm and leg movements
  • reaches and feel with an open hand
  • grasps an object crudely with 2 hands
  • waves his fists and watches them
  • lifts his head and chest while lying on his stomach
  • turns his head towards the direction of sound
  • holds his head more steadily when supported in a sitting position
  • laughs and coos

Social and intellectual development


Your baby is learning about the world. He is learning whether the world is a place to be trusted. He learns to trust and feel secure through your care. When his needs are consistently met he learns to trust.

Babies prefer their mother's voice to that of any other person. 6 to 8 weeks of age your baby will smile in response to your face or the sound of your voice. Babies as early as 1 month old may show signs of anxiety if they are cared for by an unfamiliar person.


  • A newborn can distinguish between his mother's and father's voices and the voice of a stranger by 3 weeks old.
  • Your baby can hear and can distinguish between a variety of sounds in the language spoken to him. He is rapidly learning to decipher your mood from your tone of voice and will respond accordingly e.g. he smiles when you speak in a comforting manner.
  • Babies love to look at faces and will stare at movement and lights.
  • Babies prefer bold colors to soft pastel colors.

What to expect!



Babies want to be held. Your baby would be very happy to be held 24 hours a day. His need to be held is related to the most basic of instincts - survival. Animals are genetically programmed with survival instincts, as are human infants. It will take time for your baby to learn to trust and feel secure in this strange new world, until that time your baby will frequently require the reassurance of close physical contact.


At birth your baby has reflexes as his sole physical ability. Because a reflex is and automatic and involuntary action; this means your baby cannot control his limb movements. The most obvious of the many reflex of your newborn is the 'startle reflex', in which your baby will arch his back, throw back his head and fling out his arms and legs, then rapidly draw his arms and legs to his body.


Less well known reflexes include the 'rooting reflex', where anything that brushes his cheek will cause him to turn and open his mouth and the 'sucking reflex', where anything that go into your baby's mouth, such as a finger, pacifier or nipple will cause him to suck as an automatic response .  These reflex actions will continue to have a strong influence over his feeding behavior until around the age of 3 to 4 months. As your baby's brain matures he will not only gain voluntary control over his limb movements but also this sucking reflex will fade and be replaced by a deliberate, voluntary sucking action.


For many babies the urge to suck is strong during these early months and your baby's need to suck may extend beyond his need for nourishment. For a bottle fed baby there is an increased risk of overfeeding if his sucking urge is misinterpreted as a sign of hunger.


Because a newborn cannot voluntarily control their movements they DO NOT show signs of tiredness that an older child or adult does. These signs are OFTEN overlooked or misinterpreted as pain, hunger of boredom.


Your baby will start to dribble or drool and chew his hands at around the age of 3 months.  His salivary glands are starting to work in preparation for solid foods but he's not capable of moving the saliva to the back of his mouth to swallow it. At 3 months he also has more voluntary control over his limbs; combined with his urge to suck will mean he chews his fingers and hand or anything else he can get into his mouth. These normal developmental changes that occur at this age are OFTEN mistaken as signs of teething.




Your baby communicates through his behavior. Crying is just one of the many behaviors in your baby's repertoire. It can take time to learn what your baby is trying to communicate and at this early age it's not always possible to know why he cries. His cries will sound the same only varying in intensity according to his level of distress.


The first 2 weeks after birth is a recovery period, a time of adjustment to life outside the womb. Most babies will be content to sleep and feed during this period. Your baby may cry during this time but he will quickly calm with a cuddle or feeding. Around 2 or 3 weeks of age babies generally become more aware of their surroundings and therefore become more alert and wakeful . Your baby may now start to cry for reasons other than a cuddle or hunger.


Babies notoriously become increasingly restless or irritable between the age of 2 weeks and 3 months. The amount of time babies spends crying each day peaks around the age of 8 weeks. It can be very normal for a healthy, thriving baby to cry for periods of up to 2 or 3 hours each day at this time.


Infant colic is defined as "Prolonged periods of inconsolable crying in a healthy, thriving baby". Infant colic affects approx 30% of all babies in this age group, whether they be breast or bottle fed. No one knows exactly what causes colic, although many different theories exist.


Prolonged periods of inconsolable crying and distressed behaviors such as pulling up knees and back arching are often interpeted as signs of pain. However, because a young baby's body movements are controlled by reflex actions they do not choose these actions and will display this SAME behavior when distressed regardless of whatever is troubling them. For  healthy, thriving babies irritability is RARELY due to a medical or physical reason and distressed behavior is more commonly linked with over-stimulation and overtiredness. (See Why babies become overtired.) 


Your baby's nervous system is immature. Some babies lack the ability to "shut out" unwanted stimulation and can quickly become overwhelmed . How your newborn handles the stimulation of all the new and strange, sights, sounds and sensations he faces each day depends on his temperament. In the early weeks of life as your baby's nervous system is maturing he depends on you to monitor and control the amount of stimulation he receives.




Your baby may experience many bouts of hiccoughs, particularly following feeding. Nobody knows for certain why babies hiccough. The occurrence will decrease as your baby matures.


Your baby is born with infant reflexes that are necessary to ensure his survival. 2 reflexes that relate to feeding are the 'rooting' and 'sucking' reflex, both of which assist your baby to feed long before he can deliberately suck. If these reflex actions mistaken as a sign of hunger, which they often are, there is a risk of overfeeding , particularly for a formula fed baby.


Unlike breastfeeding, where a baby can control the flow of milk from the breast, young babies CANNOT control the flow of milk from a bottle, particularly when the flow is fast. A baby may appear to hungrily guzzle a bottle of milk but the truth may be he could not stop the flow because of his suck reflex.


Your baby's digestive system is immature. His gastro-intestinal tract does NOT produce sufficient quantities of digestive enzymes necessary to break down solid foods or fruit juice. Breastmilk or infant formula is the ONLY food he needs at this age.


Swallowing air during feeding is unavoidable. Bottle fed babies tend to swallow greater amounts of air when feeding than do breastfed babies and are more likely to require regular burping. Contrary to popular belief, swallowed air has NOT been shown to be a major cause of gas in infants in many clinical studies.


Your baby has a small stomach which means he can ONLY tolerate small feeds. He need to be fed at regular intervals throughout the day and night. Because breastmilk is digested more easily than infant formula, it is common for a breastfed baby to to require more frequent feeding than a formula fed baby.


Regardless of whether they are breastfed or formula fed, 50% of healthy, thriving babies in this age group will spit up , occasionally or regularly, due to gastro-estophageal reflux (GER). Only a tiny percentage of babies experience problems related to gastro-esophagesl reflus disease (GERD). Although GERD has become a popular diagnosis for irritable behaviour, for most healthy, thriving babies spitting up will cause NO problems and is completely unrelated to irritability.


Both breastfed and formula fed babies who are exposed to large, frequent feedings are at a risk of overfeeding in these early months. Overfeeding will in turn increase the likelihood of spitting up. Overfeeding also increases the risk of gastric symptoms , such as excessive gassiess and frequent explosive, watery, bowel movements developing due to lactose overload (functional lactase deficiency) in a healthy baby who is gaining large amounts of weight .


To a lesser extent similar gastric symptoms may be seen in a baby who struggles to gain weight due to milk protein allergy or intolerance.


Gastric symptoms will understandably cause a baby discomfort, resulting in irritability and sleepless. Gastric discomfort may also cause a baby to appear hungry (because babies view feeding as providing comfort). Unfortunately in the case of overfeeding, frequent feedings contributes to gastric symptoms à which cause discomfort à which in turn makes a baby search for frequent feedings, and so a viscous cycle can soon develop. (See Hungry babies for common reasons why babies overfeed).



Your baby should have lots of wet diapers. He should provide at least 5 or more wet diapers each day. Lots of wet diapers are a good sign that he's getting plenty to drink.


Your baby's bowel movements will be different depending on whether he's breastfed or formula fed. By around the age of 4 to 6 weeks you may notice a change in the frequency of your baby's bowel movements, particularly if he's breastfed. Breast or formula fed, you may also notice that he appears to strain when having a bowel movement. These are NORMAL developmental changes that occur at this age and are not necessarily a sign of constipation. As it is also normal for crying to also increase around this time, crying is often thought to be due to constipation but the two are rarely related.


You may notice a small blood stained discharge on your baby girl's diaper, this is due to hormonalDiaper rash is more common when a baby is formula fed or once a baby starts on solid food. These change the pH (acid balance) of your baby's stools meaning they are more likely to scald his little bottom. A common cause of diaper rash in this age group can be due to a thrush infection. It is unusual for breastfed baby of this age to develop a diaper ra diaper rash may be a sign of a digestive disorder.




Although it can be common for newborns to get thier day and night sleep patterns mixed up during these early weeks, the majority of babies are good sleepers up until around the age of 2 or 3 weeks.


Even after that time some babies will remain good sleepers and will sleep anywhere, anytime. Others need parents to provide the right cues and environment conducive for sleep. Babies often learn to depend on parents help to fall alseep (because this is what parents have unknowingly taught them). For many babies this dependance becomes a sleep association that will strongly influence their sleep patterns and behavior, resulting in shorter naps and more frequent nighttime awakenings.


By around the age of 3 months some babies will sleep between 6 to 8 hours without waking for a nighttime feeding, but some may continue to wake regularly for feeding overnight until closer to 6 months.


Written by Rowena Bennett


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