When I take my baby for her check ups, her doctor uses the nail on his finger and strokes the bottom of my baby's foot. Why does he do that?

Well baby check ups are done to be sure that your baby is growing and developing on par with other babies the same age. The doctor or nurse will make note of the baby's weight, length, developmental milestones and so on. Also, just as when older children and adults go to the doctor, the reflexes are checked. When yours are checked, your doctor likely uses a reflex hammer to check around your knee and elbow. What your daughter's doctor is doing is the same thing but in a different way.

Babies up to two years old have something called the Babinski sign or reflex. When you firmly stroke the bottom of a baby's foot, the big toe should bend down and the four other toes should fan out. This is normal up to two years. We lose that reflex after two years, but it can return if there is a neurological, or nerve, problem.