Physical Growth

How Big is Baby?

A full-term baby born after nine months (38-42 weeks) of pregnancy:

  • weighs an average of 7-1/2 pounds
  • is an average of 20 inches long
  • measures an average head size of almost 14 inches when the tape measure is placed just above the ears and goes around the forehead to the largest part of the back of the head.
  • Babies have much bigger heads in relation to their bodies than older children or adults. A newborn’s head makes up 1/4 of body length. In adults, the head makes up 1/8 of total height.

Useful Info: Cold Costs Calories

When you get cold, you shiver and produce body heat by muscle activity.
Babies cannot shiver. Instead, they use a special kind of fat to make heat chemically. The calories used to make chemical heat are calories the baby should be using for growth or normal activity. Putting a warm hat on your baby on a cold day saves “go-and-grow” calories.

Brain Fact

In the 1990s, research on the developing brain made headlines and nightly news. The Decade of the Brain, as Congress officially proclaimed the 1990s, had important lessons for parents. These are discussed in “Brain Facts” throughout the Growth and Development section.

Babies are born with 100 billion nerve cells – almost all of the nerve cells the brain will ever have. Before birth, nerve cells are formed at 250,000 cells per minute.

Dental Development

Invisible Teeth

Your baby’s teeth begin to form in the third month of pregnancy. The tooth buds, which will develop into the 20 “baby” or primary teeth, form first. Next, the permanent teeth begin to form, and the primary teeth begin to calcify. This process continues throughout the nine months of pregnancy.

When a newborn comes into the world, hidden beneath the gums lies a full set of primary teeth in the process of being calcified, as well as some of the 32 permanent teeth well on their way in the process of development.

Useful Info: Growth Facts

The best predictor of adult height is the family history – the height of the mother and father. Birth size reflects intrauterine nutrition and factors associated with the pregnancy. By the end of the 2nd year, the child’s height reflects the genetic heritage.

Making Sense of the World

The five senses – sight, smell, taste, hearing, and touch – are mostly developed at birth. Your baby begins using his or her senses immediately to make sense of what is going on in the world.

Sight: Although newborns have blurry vision, they can focus fairly well on objects at about 8 to 14 inches – the distance from your baby’s face to your face when you are holding your baby in your arms.

Smell: Newborns have a very well-developed sense of smell that makes them very choosy about their favorite scent. In the first days of life, a newborn can recognize his or her mother’s natural scent and likes it best of all.

Taste: Newborns also have a well-developed sense of taste. They like sweet tastes. Nursing infants sometimes refuse to nurse when they taste garlic or heavy spices in mom’s breast milk.

Hearing: Babies can hear while they are still inside the womb. At birth, they can recognize their mother’s voice – because they have heard it for several months.

Touch: Gentle touch is a true pleasure for your newborn. It stimulates physical development while relieving stress. Fussy babies are sometimes calmed by a “baby massage” – some baby lotion warmed in your hands and gently applied to baby’s arms, legs, and back.

Brain Fact

Thanks to new imaging technology, scientists are actually able to watch the brain at work. Research confirms that the most active areas in the newborn’s brain are the areas concerned with sight, smell, taste, sound, and touch.

These areas “register” the world as the baby senses it. Then the signals are sent on to memory or emotion. In this way, the newborn connects the sight and smell of mom and dad with the pleasant memory of comfort and gentle handling.

Useful Info: All Tucked In

In the first month of life, “swaddling” soothes some babies. Bundling the baby so that the arms and legs are tucked up against the body in a flexed position recreates the natural position of babies inside the mother’s womb.

Babies who are over stimulated by their own uncontrolled arm and leg movements frequently calm down and become more alert with swaddling. If your baby protests or looks or feels warm when swaddled, unwrap your baby immediately.

Play Activities

Baby See, Baby Do

How? Hold your baby directly in front of you with your faces about 9 inches apart. Stick out your tongue. Your baby may imitate you. Try opening your mouth.

Why? Babies love to look at faces. Many times they will imitate what they see.

Emotional Development

Getting Off to the Right Start

You begin to bond to your baby even before the baby is born. After your baby’s birth, your feelings deepen and grow as you get to know your baby, understand your baby’s needs, and find pleasure in meeting those needs. You bring pleasure to your baby just as your baby brings pleasure to you. This bond between you, called attachment, provides the essential building block for a lifetime of healthy relationships.
Dads who “step right up” to the crib and get involved with the care and comforting of their newborns have the best “batting averages” for knowing how to calm babies (and mothers) in distress. Practice makes perfect.
“Hey, folks, I need a break.” When your baby uses body language such as turning or looking away or arching backwards while being held or talked to, your baby may be asking for a little space. Whimpers, cries or fussing when someone is “up close” may be saying the same thing.

Health Alert: Postpartum Depression

If you find yourself depressed after your baby is born, especially if your sadness lasts for more
than a few days, talk with your partner, your family, or friends. Be frank about your need for help.
The doctor who delivered your baby is an excellent resource for professional help.
Mothers who are sad have few smiles for their babies and may resent care giving demands. Babies may be stressed, frustrated, or confused by their mother’s unresponsiveness. Both mother and baby need help

Child Rearing Myth

If you go to your baby every time he or she cries, you will “spoil” your baby.

Child Rearing Fact

Responding to crying does not spoil babies. Babies are helpless, and they have little they can do to calm themselves. Crying is their wordless way of asking for help. By always responding to your baby’s cry for help, you make your baby feel secure and help your child develop a sense of trust. The two most important gifts
you give your baby are a sense of trust and the feeling of being safe.

Brain Fact

Your baby’s early experiences are so important that they change the structure of your baby’s brain and will have a lifelong effect on his or her ability to learn and on emotional make-up.

Healthy Habits: Handwashing

To protect your baby, be sure everyone caring for your baby knows this…
Babies need to be protected from the germs that cause infection. Because a newborn’s defense system is immature, even minor skin infections can spread through the body and become life threatening. Prevention is the answer and hand washing is the best prevention. The most effective way to wash your hands is to scrub them vigorously with warm soapy water for at least 15 seconds.*

Wash your hands before handling your newborn. Of course, you should always wash your hands when preparing food, before feedings, after diapering your baby, and after using the bathroom.

*Source: Centers for Disease Control & Prevention

The Best Seat in the Car

To protect your baby, be sure everyone caring for your baby follows this rule…
Use a rear-facing infant safety seat that is properly installed in the back seat every time your baby rides in a car.

Safety Habits: Homework Before the Baby

  • Take a class in infant first aid and CPR, including how to rescue a choking infant.
  • Give your baby the gift of a smoke-free environment. Make this a lifelong commitment for your home and family. You’ll all live longer.
  • Install smoke alarms and begin a monthly habit (every first day of the month) of checking to be sure the batteries are strong and the alarm is working.
  • Plan a safe escape route from the room where your baby sleeps. If necessary, buy (and be sure you know how to use) a window escape ladder. Keep a working fire extinguisher on every floor of your home.
  • Reset the hot water heater thermostat so that the water temperature stays below 120° F.
  • Check baby’s furniture (especially if you bought it used) to make sure it meets safety standards. For example, the weave of a mesh playpen or portable crib should have small (less than 1/4 inch) openings. Your baby’s crib should have slats no more than 2-3/8 inches apart, and the mattress should be firm and fit snugly into the crib.

Safety Habits: Home Safe Home

To protect your baby, be sure everyone caring for your baby knows and follows these rules:

  • Back to sleep! Unless your doctor tells you otherwise, put your baby to sleep on his or her back. This sleeping position reduces your baby’s risk of Sudden Infant Death Syndrome (SIDS).
  • Be sure the place you put your baby to bed is safe. Your baby should not get too cold or too hot while sleeping. The room temperature should be 65°-68° F. Always keep crib side rails up and latched. Never leave your baby in a playpen or portable crib with the drop-side down. Do not use soft bedding, pillows, comforters, soft toys, toys with loops, or string cords.
  • When changing a diaper, dressing baby, or giving your baby a bath, always keep one hand on the baby. Never leave your baby unprotected in a dangerous spot such as in a tub during bath time, on a changing table, or on a bed or sofa.
  • Prevent scalds and burns by never carrying or drinking hot liquids or smoking while holding your baby.
  • Don’t tempt fate! Never leave your baby alone with a young child or pet.

Safety Habits: Home Safety Shower

Baby gifts that help keep little ones safe are great gifts for babies and parents. The Consumer Product Safety Commission encourages safety showers by offering information on planning the shower, games and activities to play at the shower, and a 12-point safety checklist for new parents.

A baby safety shower kit may be obtained by calling the Consumer Product Safety Commission at 1.800.638.2772 or by checking out the Web site at

Health Alert: Fragile, Handle with Care

To protect your baby, be sure everyone caring for your baby knows and follows this rule…


Your baby must never be handled roughly. Sudden, jerking motions such as shaking cause violent back-and-forth movement of the baby’s head – and the brain inside the skull. Bleeding into the brain from torn blood vessels, or swelling of the tissue itself, can result in tragic outcomes – seizures, blindness, deafness, and even death.

Babies must be handled gently to prevent physical and emotional harm. Although every part of your baby’s body is fragile, your newborn’s relatively large head and weak neck muscles require very special handling. Head support is a “must” while your baby’s neck muscles are growing strong enough to hold his or her head without support.