Early childhood encompasses ages 1 to 4 years. Huge changes take place during this stage, as tiny, dependent infants transform into children who can walk, talk and begin formal learning.  

By their fourth birthday, most children attain a height that is double their length at birth. They also gain muscle control, balance and eye-hand coordination, which enable them to become more physically active and independent.

Motor skills generally achieved during early childhood development include the ability to walk, run, kick and throw a ball overhead as well as pedal a tricycle. By age 4, children can also eat, dress and undress without assistance.

Children also experience huge developmental changes in their cognitive and language abilities during these years. At age 1, most children are able to say a few intelligible words. By their fourth birthday, most children speak clearly in sentences of four to six words, have a vocabulary of more than 1,500 words and understand the concept of counting.

Healthy children develop at their own pace, and it is normal for some to achieve various developmental milestones earlier or later than others. The time frames used in this patient guide should serve as a rough estimate rather than an exact schedule of how early childhood development will unfold. Parents looking for a specific behavior at a specific time should observe the child over one month.

Failure to meet certain milestones may be signs of possible developmental delays. For example, a child who has not learned to walk by the age of 18 months may be delayed.  Other delays during early childhood years can include, but are not limited to,  failure to thrive, not being able to throw a ball overhand or ride a tricycle, showing no interest in interactive games, not using the personal pronouns “me” and “you” appropriately, not responding to people outside the family, or excessive aggression. In addition, children sometimes lose skills they had already mastered.

During early childhood – from about ages 1 to 4 years – healthy children continue growing and developing in all areas, physically, mentally and emotionally.

During infancy, babies gain weight, grow and begin all areas of development. From ages 1 to 4, this development progresses at different rates in each area. Physically, most children attain a height that is double their length at birth by the time they are 4 years old. They also gain muscle control, balance and eye-hand coordination, which enable them to master basic motor skills, such as being able to walk more steadily, run, and kick and throw a ball.

In addition to increased musculoskeletal strength, children experience huge developmental changes in their cognitive and language abilities during these formative years. By their fourth birthday, most children speak in sentences of four to six words, have a vocabulary of more than 1,500 words and understand the concept of counting.

Healthy children grow and develop at their own pace. Some children may achieve various developmental milestones earlier or later than others and still be within the normal range. Children who were born prematurely may lag slightly. Generally, by age 2, developmental differences between a premature child and a full-term one are minimal.

Parents can observe children as they reach particular milestones. Although mild delays are not a cause of concern, failure to reach a milestone may signify some type of developmental delay. In early childhood, these may include failure to thrive, not being able to throw a ball overhand or ride a tricycle, showing no interest in interactive games, not using the personal pronouns “me” and “you” appropriately or not responding to people outside the family.

Possible causes of developmental delays during early childhood include premature birth, lack of adequate nutrition, congenital conditions (e.g., fetal alcohol syndrome), autism or mental retardation. In addition to developmental delays, some children may lose skills that they already mastered, such as communicating with others. These may be related to conditions around them (e.g., birth of a sibling) or may also be signs of serious conditions such as pervasive developmental disorders.

All the stages of early childhood development can be monitored when children receive regular checkups with a pediatrician. During early childhood, the American Academy of Pediatrics (AAP) recommends well-child visits at age 12 months, 15 months, 18 months, 2 years, 3 years and 4 years.

In contrast to the rapid growth that occurs during infancy, a child’s growth rate slows down during early childhood development. Physical growth does not increase steadily during this stage. Instead, it typically occurs in spurts.

Babies usually gain between 3 and 5 pounds (1.4 and 2.3 kilograms) during the second year of life. Most 2-year-olds are about 34 inches (86 centimeters) tall and weigh about 27 to 28 pounds (12.3 to 12.7 kilograms). Boys tend to weigh slightly more than girls.

From ages 2 to 4 years, most children gain about 4 to 5 pounds (1.8 to 2.3 kilograms) in weight and 2 to 3 inches (5 to 8 centimeters) in height each year. Head size increases only by about 1 inch (2.5 centimeters) in circumference during early childhood.

Appetite typically decreases during this stage, and a child’s weight may remain the same for weeks at a time. As body fat steadily decreases during early childhood, children gain muscle tone and have a leaner, more muscular body appearance by age 4.

Toddlers usually have protruding abdomens when standing, and an inward curvature of the lower spine called lumbar lordosis. Increases in height during early childhood result primarily from growth of the lower extremities and, to a lesser extent, elongation of the trunk. Growth of a child’s lower extremities often is accompanied by a bowing of the legs. Parents should not be concerned by either lumbar lordosis or their child’s bowed-legged appearance because they typically correct themselves by a child’s third birthday. Throughout childhood, a pediatrician will continue to monitor a child’s growth in weight and height, and check for any abnormalities or growth delays.

Growth during early childhood also may be accompanied by growing pains. This is a normal occurrence that may affect children ages 3 to 5 years. Pain often affects the muscles of both legs, and may vary in intensity and duration. Children usually experience growing pains at night, and symptoms generally go away by morning.

By age 2, vision is fully developed. Most healthy children have 20/20 vision and can see details as well as all colors. A child’s hand preference is also well established at this time.

All primary teeth typically have emerged by age 3. The American Dental Association (ADA) recommends that beginning at age 3, children use toothpaste that contains fluoride to support healthy teeth and gums. In addition to routinely brushing teeth with fluoridated toothpaste, children can decrease risk of cavities by drinking water with fluoride.

Most 3-year-olds, especially girls, have control over their bowel and bladder functions during the day. Nighttime control usually occurs slightly later. Parents and other caregivers may start toilet training their toddlers as early as age 2, although some may wait until a child’s third birthday. Bedwetting is normal up to age 4 in girls and 5 years in boys.

During the second year of life, babies who have not started walking generally do so around age 15 months. At first, toddlers typically move their legs wide apart and appear to hesitate between steps, jerking or swaying from side to side as they put one foot forward, then the next.

About six months after taking the first steps, toddlers develop a more adult-like walk – holding their hands at their sides, as opposed to the front for balance, and moving with their feet closer together. They also move their feet from the heel to the toe when walking.

Children frequently fall as they learn to walk. Parents can reduce risk of injury to their toddlers by having them walk on soft carpeted surfaces and removing or covering objects or furniture with sharp edges.

As children begin to walk more steadily, they usually enjoy taking on new challenges such as picking up, carrying and throwing objects, moving while pulling a toy behind them and climbing stairs. Most children can run, jump in place, stand on tiptoes as well as kick and throw a ball overhand by age 2.

Around this time, toddlers are often able to climb onto and down from furniture without assistance. They can also scribble, build a tower of four or more blocks and turn over containers to pour out contents.

By age 3, toddlers have achieved greater balance. They can balance on one foot for brief periods and are able to walk up stairs with alternating feet and pedal a tricycle. They can also bend over easily without falling.

Fine motor skills associated with this stage include being able to turn pages one page at a time, as well as turning doorknobs and pushing small objects through small holes. To promote safety, any household rooms that are not childproof should be kept locked at all times. To prevent poisoning, all household cleaners, chemicals and medications should be stored out of a toddler’s reach.

By their fourth birthday, most children are able to feed themselves without difficulty and dress without assistance. However, they may need help with shoelaces, buttons and zippers.

They continue showing improved balance and more agility. They can now hop on one foot without losing balance for longer periods. By age 4, children are able to throw a ball overhand with improved coordination and can catch a bounced ball most of the time.

A 1-year-old’s brain has matured enough to allow babies to recall past actions and events. As memory becomes more established, toddlers are able to learn from what they have seen other people do. For instance, a toddler may watch a person do something and then try to repeat the action later in the day or even a week later.

During early childhood development, toddlers are learning to appreciate how certain sounds, sights, smells, tastes and textures go together. Although the sense of smell is fully developed at birth, most children become aware of the difference between pleasant and foul odors around age 3.

Studies show that toddlers thrive in an environment rich in sensory stimuli. Toddlers respond to music by singing along to a song or marching and playing drums or other play instruments.

By 18 months, toddlers like to play repetitively (e.g., throwing a ball) for long periods of time. Repetition allows them to pay attention to what they are doing and learn from it. At this stage, toddlers do not require formal teaching to develop their cognitive skills. Parents or other caregivers can promote learning by listening attentively, talking often and recognizing the types of activities that interest the child.

Beginning at age 1, a baby’s babbling gradually transforms into a few simple words. A child’s first few words usually involve the name of a person, object or action. They also typically include, “hi” “bye-bye” and “no.” Most toddlers speak anywhere from 20 to 50 words by age 20 months. Around this time, a toddler's brain becomes more focused in the way it responds to language. Speech is processed more rapidly, enabling children to better understand. Toddlers can understand more language than they can express at this age.

Toddlers at this stage can point to objects or ask what they are. They enjoy simple songs, finger plays and games involving sounds and words (e.g., patty-cake). They also like practicing new words or phrases, usually before falling asleep at night or while riding in a car.

Language development varies by several factors. The number of words toddlers are able to say by their second birthday is related to many factors including gender, whether they are outgoing or shy, and whether they are part of a small or large family. Children’s surroundings may also influence their language development. For example, a child may talk more if spending more time with adults or communicate less if spending more time with other children. With older siblings, a toddler may not need to speak often if the other children talk instead. Girls are usually more advanced than boys in language abilities.

By age 2, most toddlers have an increased attention span and can often say about 300 words, including their name. They can usually point to named body parts and name pictures of items and animals. Most 2-year-olds can also form phrases of two to three words, such as “more juice” or “give me cookie.” This enables them to communicate needs, such as hunger and thirst. Many parents begin toilet training when the child is able to express a need for a diaper change or to use the toilet.

After language skills develop, toddlers incorporate it into their play. During early childhood development, a child’s play will gradually become more sophisticated, and they usually like to imitate other people by playing with play food, dolls and dress-up clothes. Most toddlers after age 2 understand that toys are symbols of things in real life.

By age 3, a child's brain is about 80 percent of adult size. Language and movement skills continue to increase dramatically, supporting a toddler's intellectual and language development. Pronunciation should also be improving steadily, and a child’s speech is generally more understandable at this time. Most 3-year-olds can compose sentences of three to five words and frequently ask questions.

Other milestones many children accomplish by age 3 include the ability to make mechanical toys work, match physical objects to pictures of the objects, sort objects by shape and color and complete puzzles with three to four pieces. Around this time, children also begin to engage in imaginary or make-believe play with dolls, animals and people. Children at this age may have imaginary friends. Make-believe play is a normal facet of early childhood development.  

By their fourth birthday, most children have a vocabulary exceeding 1,500 words. They can easily compose sentences of five to six words and are able use the past tense. Most children can say their age and sex when asked as well as correctly name some colors. Most 4-year-olds are also developing an understanding of time and are able to distinguish between two objects based on size and weight. They generally also understand the concept of counting and are able to count up to four. By age 4 or 5, memory increases further and children are able recall parts of a story. They usually also enjoy telling stories to entertain others.

Emotional and social – psychosocial – development in early childhood includes children learning about social roles and how to interact with others through the use of language.

Around age 12 to 18 months, most toddlers are able to understand that certain behaviors (e.g., biting, hitting, screaming) are socially unacceptable. However, they are often not able to control their urges and impulses. Although it may be difficult at first, by age 2 many toddlers can begin to learn to control some of their socially unacceptable behaviors when they are consistently shown how to do so by a parent or other caregiver.

Two-year-olds sometimes can restrain themselves when told “no.” However, toddlers frequently test the limits of parents or caregivers and ignore such commands. Children typically have difficulty controlling themselves when they are tired, hungry or upset, which is usually when temper tantrums are most likely to occur. Temper tantrums enable toddlers to learn how to cope with difficult situations.

Words become increasingly important for behavior control during early childhood. Parents and caregivers can explain more to children as the children learn to understand more.

Although corporal punishment (e.g., spanking) is a common method used to discipline children, most childhood health experts strongly discourage it. According to the American Academy of Pediatrics (AAP), spanking children frequently during early childhood may be associated with behavior problems during middle childhood.

Children also display a sense of humor at a very young age. Sometime between 9 and 15 months of age, babies know enough about their environment to grasp that when an adult barks like a dog, makes a funny face or does something else unexpected or silly, it is funny. As they get older, toddlers appreciate physical humor, especially when there is an element of surprise (e.g., being tossed up into the air by an adult). As they develop their speaking skills, verbal humor becomes a great source of amusement. They will find rhymes and nonsense words funny and this tendency will continue well into early and middle childhood.

By age 2, most toddlers become increasingly aware of themselves as separate from others. One of the signs of this growing awareness is the emergence of words, such as “me” and “I,” in their vocabulary. Along with an increasing awareness of the self come issues of ownership and sharing objects, especially toys.

Toddlers are typically self-centered and often display a strong possessiveness with objects and toys, claiming them as their own. Though this behavior usually makes toddlers appear selfish, once they become more secure in knowing what is and is not theirs, they gradually begin sharing more readily with other children.

Toddlers commonly display a wide range of feelings. Sometimes these feelings can be very strong. They may feel proud of a tower they have built but get very frustrated and upset when it tumbles to the ground or angry if someone topples it over. A toddler’s emerging independence is often mixed with still wanting to be cared for like a baby. For instance, a 2-year-old may want to do everything alone one minute, but want to be held in the arms of the parents the next.

Separation anxiety, which usually begins around age 10 to 18 months, generally goes away during the last half of a toddler’s second year as the child become increasingly enthusiastic about the company of others, especially children. By age 3, most children can separate easily from parents. A toddler’s behavior can vary, depending on temperament. At this stage, a parent’s or other caregiver’s emotional responses and social interactions serve as a model for the child to imitate.

Starting at age 3, children typically begin acting out social encounters through play activities such as playing “house.” They are also increasingly inventive in fantasy play.

Some children enjoy lots of noises and sights, though others need a little less excitement. All children have their own unique style and way of learning.

Most 3- and 4-year-olds crave new experiences, show affection openly and usually are more cooperative when playing with other children. Around this time, healthy children may be curious about the naked body and genitals. For instance, children may “play doctor” and show their body parts to other children and vice versa during such games. Masturbation is also normal at this time. However, masturbation that has a compulsive quality or that interferes with a child’s normal activities may be a sign of sexual abuse in children.

According to the National Institutes of Health (NIH), the leading cause of mortality among healthy children age 1 to 4 is accidents, especially those involving automobiles. Other top causes of accidental death in children include drowning, fire, falls and poisoning. Child safety is extremely important for toddlers and young children. Car safety should be enforced at all times, even when traveling short distances. Children 4 years old and younger should always be strapped into a car seat placed in the backseat of a vehicle before driving.

Because of their increased mobility, toddlers and older children are at greater risk for accidents and injuries. Just as during infancy, parental supervision along with a safe home environment continues to be essential at this stage. Young children should never be left unattended – even for short periods – or with siblings or pets. To prevent poisoning, all household cleaners, chemicals and medications should be stored out of a child’s reach.

Children also may be prone to accidents or injuries (e.g., fractures) while playing. Playground safety should be enforced. Parents and caregivers should also introduce and enforce rules about not playing in the streets or crossing these without adults. Keeping a well-stocked first-aid kit as well as a list of important phone numbers (e.g., Poison Control Centers, neighborhood hospitals) handy in case of an emergency is also recommended.

Other ways parents and other caregivers can promote healthy early childhood development include:

• Encourage physical activity. Health experts recommend that toddlers participate daily in at least 30 minutes of structured physical activity such as playing on the playground or playing with a ball. Toddlers should not be sedentary for more than one hour at a time, except when they are sleeping. Three- and 4-year-olds require at least one hour of physical activity a day.
  
  
• Stimulate learning and play. Provide children with safe, age-appropriate toys that stimulate learning including simple puzzles, stacking toys, sculpting clay and paper and crayons for drawing. Most toy manufacturers label new toys for specific age groups.
  
  To help develop social skills, encourage them to play with other children and instruct the child on how to participate in and learn the rules of sporting activities and other group games. Sing, recite nursery rhymes and play hand games (e.g., patty-cake) with a toddler. These are fun activities that can encourage learning. For example, singing the ABC song can help a child learn the alphabet.
  
  
• Nurture language development. Converse with and read often to a child – at least once a day. Read slowly enough for a toddler to understand, as well as expressively, using different voices for different characters and raising or lowering the voice as appropriate, to make it more enjoyable for the child.
  
  Discuss the story or book. Ask the child to name objects in the illustrations and ask open-ended questions about the story, such as “What do you think will happen next?” Doing so will encourage a child to think about the story and ask questions about it.
  
  
• Be a positive role model. Teach children the concepts of saying please, thank you and sharing with others. Also, when teaching appropriate versus inappropriate behaviors, parents should be consistent to avoid confusing a young child.
  
  
• Offer children lots of praise to encourage self-esteem.
  
  
• Limit the time and content of television viewing. The American Academy of Pediatrics (AAP) does not recommend television for children age 2 or younger. For older children, the AAP recommends no more than one to two hours a day of educational, nonviolent programs.
  
  
• Allow children 3 years old and older to participate and help out in daily household activities. This will encourage learning as well as teach a child to be more responsible and efficient.
  
  
• Expose a child to different stimuli. This can be accomplished by visiting areas of interest, such as a zoo, park, beach or children’s museum.

Preparing questions in advance can help parents have more meaningful discussions with their physicians regarding their child’s growth and development. Parents may wish to ask their child’s pediatrician the following questions about early childhood development:

1. What milestones should I watch for and at what ages?
   
   
2. How long should I wait after noticing a developmental delay before calling?
   
   
3. My 18-month-old makes no attempt to walk. Is this normal?
   
   
4. My 2-year-old has become a picky eater. What can I do to get her to eat more?
   
   
5. When I give simple commands to my 2-year-old, such as give me the bottle, he does not understand me. Is there something wrong?
   
   
6. Will my toddler experience milestones at the same ages as his older siblings did?
   
   
7. My 3-year-old has very unclear speech. Is this indicative of a speech impediment?
   
   
8. Should I be concerned if my twins do not reach milestones at the same time?
   
   
9. My 4-year-old still experiences separation anxiety. Is this normal?
   
   
10. Are there any signs that I should be on the lookout for that may indicate a learning and/or developmental problem in my child?