Exactly what is a “growth spurt”?

The term “growth spurt” (also called frequency days) describes times when babies seem to nurse non-stop for a couple of days. It is believed that this is how the baby tells the mother’s body to increase milk production. Babies usually have several “growth spurts” in the first 6 months.  They often occur at 10 days, 3 weeks, 6 weeks, 3 months and 6 months. But they can occur any time.  After about 48-72 hours of frequent nursing, a baby will return to a more regular routine of nursing, rest and playtime.