First breath

One of the most significant biological changes after birth is the baby’s first breath. As the child emerges from the womb and encounters the outside air, their lungs expand, and they take their first breaths independently. Previously, with the baby oxygenated in utero, the lungs are quite densely packed and largely unused.

Clearing of airways

As the baby takes their first breaths, any remaining amniotic fluid or mucus in their airways is usually cleared out, helping establish clear and unobstructed breathing. This is a key moment for medical staff in attendance, who are well trained to spot the signs of obstructed air passages before asphyxiation sets in.

Circulation changes

With the cutting of the umbilical cord, the baby’s circulatory system undergoes a major shift. Instead of the flow of nutrient-rich blood being drawn from the placenta, it instead circulates to the lungs, and the baby’s heart starts pumping blood to oxygenate the body independently.

Skin color changes

When a baby is born, its skin will have a distinctly blue, purple or dark red hue. Once the baby starts breathing on its own, its skin will gradually change to a more normal shade of pink. This process generally takes somewhere between five and seven minutes, but hands and feet might remain discolored for up to 24 hours.

Heart rate stabilization

Immediately after birth, the baby’s heart rate adjusts to regulate blood flow and oxygenation throughout the body. It may initially be rapid as the baby’s organs and muscles oxygenate but typically stabilizes within a few minutes. This is why babies are initially born a dark red or purple color, which then fades within the first day.

Temperature regulation

As babies transition from the warm environment of the womb to the outside world, their bodies begin to regulate their own temperature. Skin-to-skin contact with the parent helps maintain the baby’s body temperature. It also serves to relax the baby as these many biological processes take effect.

Crying starts

Almost immediately after birth, babies begin emitting the trademark, piercing cry of a newborn. While this can sound distressing, it’s completely normal. After crying for a few minutes, most babies will settle into silence, stare around them for a few moments and then fall fast asleep.

Colostrum production

Within the first few minutes after birth, and no earlier, the mother’s body begins producing colostrum, colloquially known as early breast milk. Colostrum is rich in antibodies and essential nutrients, providing the baby with initial nourishment and immune support, which babies seek less than an hour after birth.

Contraction of the umbilical vessels

After the umbilical cord is clamped and cut, the blood vessels within the cord constrict, helping to prevent excess bleeding and promote the transition to independent circulation. However, it takes 10-14 days for the umbilical cord to detach entirely; in some cases, it can take as long as 21 days.

Glucose regulation

The baby’s body starts regulating blood glucose levels independently after birth. The baby’s liver begins to produce glucose and manages its levels to meet the energy needs of the body. In a healthy baby, it only takes two to three days for glucose production to rise to a level that will be sustained into adulthood.

Brown fat begins to burn

A baby in utero produces roughly twice as much heat as an adult. After they are born, babies rapidly begin losing heat, which is detected by nerve cells in the skin. This initiates a number of physiological responses designed to maintain body temperature, including the burning of brown fat reserves.

Reflexes develop

Amazingly, various reflexes are observed shortly after birth, such as the rooting reflex (turning towards touch on the cheek) and the sucking reflex (initiating sucking motions when something touches the roof of the mouth). These reflexes, entirely unnecessary within the carefully managed system of the womb, aid in feeding and survival instincts.


Around 90 percent of newborn babies develop a sucking habit within the first two hours of their lives. While the purpose of this sucking instinct is to enable them to feed, newborns will frequently suck their thumbs, the corners of their blankets or anything else that happens to be in their vicinity.

The liver starts to break down waste

While all of a baby’s internal organs have long been fully developed by the time it’s born, many of these organs don’t start fully functioning until birth occurs. Shortly after a baby takes its first breaths of air, its liver starts processing and breaking down waste products, including excess red blood cells.

The immune system starts to develop

Wombs are relatively sterile environments, so babies won’t have had to fight off any pathogens before they are born. This all changes with birth. Babies’ immune systems start rapidly developing as soon as they are born, although they will still be vulnerable to bacteria and viruses for some time.

Kidneys begin regulating fluids

Between nine and 12 weeks into pregnancy, unborn babies will have almost fully kidneys that are already forming urine. The kidneys continue in this function after birth, but they also begin regulating the balance of fluids and electrolytes within the baby’s body, which assists with hydration.

Hormonal changes

Birth triggers various hormonal changes in the baby’s body. The stress of labor and delivery stimulates the release of hormones such as cortisol and adrenaline, which help the baby adapt to the new environment by increasing alertness, initiating lung expansion, and preparing the body for independent functioning.

A vitamin K injection can prevent haemorrhagic disease

In many parts of the world, babies are given a vitamin K injection shortly after birth. This is to prevent haemorrhagic disease, a rare but serious condition caused by vitamin K deficiencies in newborns. While it can seem cruel to inject a baby straight after birth, the procedure causes minimal distress.

Falling straight to sleep

Even when everything goes smoothly, birth is quite an ordeal for a baby. It’s therefore not surprising that, soon after entering the world, most babies fall into a deep sleep. This sleep can last for a considerable length of time, which sometimes unnerves new parents, but it’s completely normal.

Voice recognition will begin

Babies are able to recognize their mother’s voice as soon as they’re born, which makes sense considering they’ve been listening to it since their ears developed in the womb. If the father has been regularly speaking to the baby while it’s in the womb, it will likely be able to recognize his voice as well.

Vision will remain blurry

Babies open their eyes within a few minutes of being born, but that doesn’t mean they can see what’s going on around them. For the first few days of a newborn’s life, most of its field of vision will be completely blurry, although it will just be able to make out your face while you’re feeding it.

Certain tastes can be recognized

While it will take years for their sense of taste to fully develop, babies are able to recognize certain flavors right from birth. Specifically, they will be able to detect the flavor of their mother’s milk, which is similar to the amniotic fluid it has spent the last nine months suspended in.

Digestive system starts functioning

Within their first 24 hours outside of the womb, most babies will pass urine and have a bowel movement. Newborn feces are known as meconium, and they are black and tarry. Again, this can freak out first-time parents, but there’s nothing to worry about, and the baby’s bowel movements will start looking more normal within a few days.

Microbiome starts forming

When a baby is born it is exposed to a significant amount of new bacteria, which will form the basis of its microbiome. Additional bacteria will be introduced through breastfeeding, and after a few days most newborns will have a thriving, healthy microbiome established in its gut.

The brain starts growing

Humans have incredibly large brains relative to body size, and this poses problems when it comes to birth. In order for the head to be able to pass through the birth canal, babies have to be born with incredibly underdeveloped brain, which is why humans are born so much more helpless than other animals. As soon birth is complete, however, the brain will start growing.

Weak neck

Babies are born with incredibly underdeveloped neck muscles, which means they have a hard time controlling the movement of their heads. As a result, newborns often rest with their heads tilted in a way that looks unnatural, but is actually completely normal and not a cause for concern.

Feeding and sleeping patterns develop

In the days following a baby’s birth, there won’t be any discernible pattern governing when it wants to eat or sleep. Gradually, however, the baby will settle down into a mostly predictable routine, eating at around the same times every day and falling asleep shortly after, much to the relief of its parents.

Fists will usually be clenched

One of the first things babies do with their hands is form them into tight fists, which is due to a neurological reflex known as the palmar grasp. In the first few days of a baby’s life this action will mostly be random, but it will soon become a sign that the infant is hungry.

Sleeping in four hour blocks

For the first few months of their lives, babies will generally sleep for around 16 hours a day. This is typically broken up into roughly four hour blocks, in between which babies wake up to feed. It’s important to note, however, that not all babies will follow this structure, and you shouldn’t try and impose a routine onto them.

Skin hair falls off

Some babies are born with a covering of fine hair – which is known as lanugo and can be either dark or fair – affecting a large portion of their skin. This is particularly common in preterm babies. Lanugo generally disappears on its own, normally within the first few weeks of the newborn’s life.

Cradle cap

New parents frequently notice thick, scaly flakes which have a waxy feel on their newborn’s head. This condition – which is known as cradle cap – is extremely common, and it’s caused by skin changes following birth. Cradle cap generally goes away within one to two weeks.

Urination will increase

Babies will generally urinate just once in the first 24 hours after their birth, but the number of times they urinate a day will steadily increase. By their sixth day, babies should be urinating an average of six times a day. A bit of variation is normal, but if they’re urinating considerably more or less often you should consult a doctor.

Babinski reflex

The Babinski reflex is one of the reflexes that newborns possess from birth. To test the Babinski reflex, a doctor will stroke the baby’s sole from the heel up, which should cause the big toe to point up while the other four fan out. Babies with intellectual disabilities may hold this position for an abnormal length of time.

Head shape changes

Babies are often born with slightly cone-shaped heads. This is because their skulls are made up out of individual segments, which allows their heads to compress as they pass through the birth canal. Over the first week or so of their life, however, their heads should round out.

Facial swelling goes down

Babies are often born with swollen – and sometimes even bruised – faces, the result of the pressure they have to endure during birth. This swelling will gradually subside over the next few days, and should be completely gone by the end of their first week at the latest.

There may be nipple discharge

Newborn babies sometimes exhibit a milky discharge from their nipples, normally accompanied by slightly enlarged breast tissue. While this can seem incredibly strange, it isn’t a cause for concern. The reason for this discharge is elevated levels of estrogen or prolactin in your newborn’s blood, and it should resolve in a week or two on its own.

The remains of the umbilical cord fall off

When the umbilical cord is cut after birth, a section of it will remain attached to your baby. This will turn black and fall off of its own accord, usually around 10 to 14 days later. Once the cord drops off it will leave a slight wound that will form into the navel as it heals.

Blocked tear ducts

One of the most common issues newborn babies experience is blocked tear ducts. This usually manifests as stick eyes fill with gunk, or discolored discharge. Blocked tear ducts can normally be effectively treated at home with a combination of eye rinses and gentle massages, although you should speak with your doctor to be on the safe side.

Startle reflex is fully formed

Babies are born with a number of instincts fully formed, one of which is their startle response. While your newborn will generally seem pretty impassive to events around them, you’ll likely notice that they visibly react to loud sound, often responding with a sudden movement and orienting themselves towards the noise.

Baby b egins to settle down

Once a newborn baby starts crying, there’s not a lot that can be done to stop it. Within a remarkably short amount of time, however, babies will become much more receptive to efforts to comfort them. That said, there will still be times when your baby cries for seemingly no reason, and resists all attempts to calm it down.

Crying for attention

While it will usually take between 12 and 18 months for babies to start talking, they will be able to let you know when something is wrong almost from the moment of birth. Babies use cries to indicate that they need something, with the intensity of the cry normally linked to the level of discomfort the baby is feeling.

Jerky movements in sleep

Babies spend a lot of time asleep, and this is especially true of newborns, who will normally spend well over half the day unconscious. That doesn’t mean they’ll be resting peacefully, however, and you’ll probably observe your newborn making lots of jerky movements in their sleep, which is the result of their nervous system not being fully formed.

Losing weight is natural

If you notice that your newborn is steadily losing weight, don’t panic. It’s completely normal for a baby to lose up to ten percent of its bodyweight within its first week of life, and it will start putting it back on after this point. If the weight loss continues, however, you should seek medical advice.

Rashes might be a common occurrence

Rashes are incredibly common in newborns, and most of the time they aren’t anything to worry about. Oftentimes the rash will have an obvious cause, such as irritation from diapers, but this isn’t always the case. It’s always best to have rashes checked out by a doctor, just to be on the safe side.

Pupils dilate

If you look into your newborn’s eyes shortly after birth, you will notice that it has minuscule, pin-prick pupils. This is to limit the amount of light that can enter the baby’s eyes, which are completely accustomed to the darkness of the womb. After around two weeks, your baby’s pupils will begin to noticeably dilate.

Vision improves

Over the first couple of weeks of your baby’s life, their eyesight will steadily improve. You can help the muscles in their eyes get stronger by moving your head slightly as your baby feeds, which should make them move their eyes from side to side.

Rapid brain development

While a baby is born with almost all of the neurons it will ever have, its overall brain size will begin developing rapidly. In the first year of its life, a baby’s brain will double in volume – a rate of growth much faster than any other part of its body – and by the age of three its brain will have reached 80 percent of its adult size.

Sense of smell improves

As little as ten weeks after conception, a baby’s smell receptors have already formed, and it will soon be able to detect the smell of amniotic fluid. Smell is also one of the fastest senses to improve after birth, and at only a few days old a newborn will be able to differentiate between the scents of its mother and a stranger.

Eyes will start moving

While babies are able to move their eyes from side to side shortly after being born, they won’t do so with any particular for intent for a couple of weeks. As their ocular muscles strengthen, however, and their vision improves, babies will begin moving their eyes to track their parents as they move around them.

Baby begins to vocalize

Even though your baby won’t start talking for 12 to 18 months after it’s born, it will start experimenting with its voice a long time before that. For the first couple of weeks your newborn will mostly just cry, but after that you will notice it starts making “ooh” and “ah” sounds when it’s content.

Movements become smoother

About five weeks after they are born, a baby’s movements will start to become less jerky as their neurological circuits continue to develop. You can speed this process up by actively playing with your baby and encouraging them to move, and by giving them objects to hold in their hands.

First smiles

After only around six weeks, your baby will start to flash an adorable, toothless smile. This will be accompanied by a widening of the eyes, and it will often occur when your baby sees its mother, father or someone else whose presence it has grown accustomed to.

Deliberate head turning

For the first few weeks of a baby’s life, it will only turn its head in reaction to external stimuli, for example loud noises or bright lights. As it develops, however, it will begin moving its head of its own volition, and you might notice its gaze following you as you move around the room.

Head starts to raise

As babies begin regularly turning their heads, their neck muscles will strengthen and develop rapidly, and after a few weeks they will be able to lift up their heads while they are lying on their stomachs. This is an important stage that babies will need to master before they can attempt to crawl.

Baby will start to reach

After around two months of life, babies will become more aware of items in their vicinity, and may even start reaching out for them. Their attention normally won’t last for more than a few seconds, and if they can’t grasp what they’re reaching for they will quickly move on to something else.

Spitting up

Newborn babies often spit up a small amount of milk after they’ve finished feeding, sometimes while making a choking sound that can be incredibly alarming. This behavior is nothing to worry about, however, and is caused by the fact that the baby’s digestive system still isn’t fully formed.

Frequent sneezing

Credit: Jeroen via Flickr

Newborns often sneeze frequently, which helps them clear their nostrils. While this can be concerning for parents who assume that their baby has contracted a cold or flu, sneezing can be safely ignored unless it is accompanied by other symptoms of illness, such as fever or cough.

Voice recognition begins

While a newborn comes out of the womb able to recognize its mother’s voice, it initially can’t distinguish between the voices of anyone else. This only takes a couple of weeks to change, however, as the circuits in the baby’s brain responsible for processing sound develop rapidly, allowing it to recognize and differentiate between the voices it most often hears.

Synaptic density increases

While a baby is born with most of its neurons already there, the density of its synapses begins increasing at an astonishing rate soon after birth. The rate of this increase begins to slow throughout childhood, and by the time adulthood is reached, synaptic density will have started reducing.

The step reflex is developed

If you notice that your newborn appears to be attempting to walk when you’re holding it upright, don’t get too excited. While you might assume that your baby is way ahead in its development, in reality it’s just exhibiting what is known as the stepping reflex, which all babies are born with.

Frequent hiccups

Hiccups are a normal occurrence in newborns, and they can sometimes last for hours. Fortunately, they won’t cause any harm, and most of the time won’t be distressing for the baby. You might be able to bring an end to a bout of hiccups by cuddling your baby, changing its position or giving it a pacifier to suck on.

Rolling over

Between two and four months after they are born, babies should start attempting to roll from their stomachs to their backs. It will likely take quite a few tries for your baby to successfully complete this maneuver, and they will probably get stuck on their backs the first few times they manage to roll.

Bones start fusing

When a baby is born, its skeleton consists of more than 300 individual bones. By adulthood, however, that number will have reduced to 206. This is because many of a baby’s bones will fuse together as its develops, a process which begins immediately after birth.

Soft spots on skull harden

Because a newborn’s skull consists of multiple segments, there are certain places where there is no covering of bone. These spots are known as fontanels, and they feel noticeably soft to the touch. After a few months, the skull plates will begin to fuse, and the fontanels will disappear.

Eye color changes

One of the most dramatic physiological changes that you will likely notice in your newborn is a change in eye color. This process normally begins around the six month mark, and – after a few weeks of gradual darkening – you might suddenly realize that your baby’s eyes have changed to a completely different color.

Adult teeth begin forming

Babies are born with a full set of primary teeth (commonly referred to as baby teeth), which will generally start emerging after three months. At around the same time, their bodies will start producing their adult teeth, starting with the central incisors. At around six years of age, the primary teeth will begin to fall out, making room for the adult set to come through.

Digestive lining increases

When babies are born, their digestive systems are very vulnerable to infection, which is why they should only drink breast milk or formula. Within a few months, however, babies develop a thick lining of mucus in their digestive systems, which protects against harmful pathogens. This process takes about six months to complete.

Sitting strength will start to develop

Before a baby is able to sit up unassisted, it needs to significantly develop both its musculature and its sense of coordination. Remarkably, this takes only around six months, after which a baby will have both the strength and bodily control to raise itself into a sitting position without falling back down.

Digestive enzymes are produced

At around six months of age, babies start producing enzymes that allow them to digest simple starches. A month or so later, they will start producing different enzymes, capable of breaking down complex carbohydrates. Finally, babies start producing bile salts and lipase, which aid in the digestion of fats.

Kneecaps start forming

When babies are born, their kneecaps consist solely of cartilage. As they start drinking milk, they absorb calcium which begins a process known as ossification, in which this cartilage begins turning into bone. By the time they are two years old, their kneecaps will have hardened significantly, and by the time they are six years old, the process will be complete.