What are the signs of a growth spurt?

Q: How can I tell if my baby's having a growth spurt?

A: Your baby will grow more during his first year than in any other period of his life, and these increases in weight and height aren't slow and steady -- they appear to happen in fits and starts known as growth spurts. Some experts think growth spurts happen at predictable ages, like 10 days, 3 weeks, 6 weeks, 3 months, and 6 months (lasting anywhere from two to seven days at a time), while others claim that there's no set schedule, and timing can vary from baby to baby. Either way, there are definite signs your baby may be going through a growth spurt:

• Your baby's hungry all the time. Pediatricians agree that a sudden increase in appetite is one of the most telling signs of a growth spurt. It's not uncommon for a baby who was nursing well at regular intervals to start suddenly wanting to spend the entire day on the breast or for a formula-fed baby to seem dissatisfied after finishing a bottle, for example.• Your baby's fussier than usual. The most obvious reason for this is lack of sleep, because your baby may be waking up more during the night to feed, which inevitably leads to fussiness during the day. Rest assured, the mood swings won't last long.• Your baby wants to sleep a lot. After several days of gorging himself, your baby may sleep more soundly than usual -- and that's when experts think growth occurs. In fact, research has shown that almost 80 percent of growth hormones are secreted during sleep. During this time, don't force your baby to stay awake or adhere to his normal sleep schedule -- you'll only make him crankier.

Remember, though, that these growth spurt symptoms can also be signs of other conditions, like teething or illness. If you have any questions about changes in your baby's behavior, it's always best to check in with the pediatrician. --Clara Ogden

Originally published in the May 2005 issue of Parents magazine. Updated 2009.