When should a baby be able to smile?

My daughter's first smile is registered in my memory as one of the most thrilling moments of my life. It came at roughly four in the morning. My body ached, my eyelids drooped, my breasts throbbed, my stomach growled, my throat was parched, I hadn't showered in three days -- and there I was, crying, myself, while trying to console my three-week-old daughter's seemingly endless screams. After I finally got her cleaned, fed, burped, and consoled, she looked up at me and rewarded me with a big, gummy grin.

Babies vary tremendously in when they first begin smiling -- with some smiling nearly immediately after birth, and others not smiling until three months old or later. If you're wondering when your baby will start smiling, here are some points to consider.

1. Babies have a few different kinds of smiles. A baby's earliest smiles, which may occur just hours after the baby is born, often aren't smiles at all, but reflexive grimaces that occur independently of the baby's emotions. Later, what I call a "happy" smile -- which I log as my daughter's first -- will occur as part of the calming reflex. Still later, a baby will develop a "social smile," which occurs in response to social stimulation such as talking, eye contact, or singing.

2. Don't expect your baby to smile as a newborn. Although some newborns do smile, early smiling isn't actually typical. Most babies begin smiling socially at around six weeks of age, doing so regularly by twelve weeks, according to Dr. David Geller. Although you may be eagerly awaiting your baby's first smile, you probably won't get to see it during the first few weeks of your baby's life.

3. It has little to do with your baby's happiness.

If your baby doesn't smile frequently, or doesn't smile early, it doesn't mean she is unhappy. Smiling isn't an emotion; it's an expression of emotion. Babies develop identifiable facial expressions at widely variable paces. While your baby may feel happiness and contentment most of the time, she may not yet have developed the physical response associated with revealing those emotions.

4. Premies will usually smile later. Like most milestones, smiling occurs later than average among premature babies. Premies are, biologically, still younger than full-term babies born at the same time, so it is perfectly normal for them to reach milestones slightly later in infancy. If your baby was born preterm, expect her to smile a few weeks later than average, but discuss it with your pediatrician if you are concerned.

5. Get in touch with an expert if you see warning signs.

Rarely, an inability to smile can be a sign of an underlying problem. If your baby is twelve weeks of age or older and still unable to smile, talk to his pediatrician to investigate for underlying medical causes. It is possible that a neurological disease or congenital abnormality is responsible for the delay. An early evaluation from your pediatrician can either mitigate your concerns or appropriately address the problem at hand.