Infant growth can be a confusing topic for new parents, says Claire McCarthy, M.D., assistant professor of pediatrics at Harvard Medical School. Here, her common-sense guidelines for how much, and how fast, your baby should be growing.

Don't get hung up on weight gain.  A newborn will lose up to 10 percent of his body weight in the first week or so after birth, but then quickly gain it back. From there, pediatricians expect infants to double their birth weight by the 4-month checkup and triple it by their first birthday.

Charts are a good start.  Your pediatrician will monitor your baby's growth on height and weight charts. Each checkup should show an upward curve throughout the year with no sudden jump (say, from the 10th percentile to the 50th) at any one time.

Genes play a role.  While height and weight percentiles are usually in the same ballpark, genetics play a big role. A baby in the 90th percentile in height and only the 50th in weight won't surprise your pediatrician if Dad is or you are also tall and lanky.