It’s one of the more bewildering baby behaviors you’ll see: Your baby scrunches up her tiny features and wails deafeningly—but not a tear trickles down her cheek.

Newborns don’t shed tears because their tear ducts haven’t fully formed. But after about a month (once the ducts have had a chance to develop), why do babies sometimes cry with tears and sometimes without?

In general, tears indicate that your baby’s feeling especially frustrated or is in some kind of pain, explains Jennifer Shu, M.D., coauthor of Heading Home With Your Newborn.

“Babies cry for many reasons—they’re tired, uncomfortable, bored, hungry. It’s their only way to communicate their myriad emotions,” says Dr. Shu. So no tears probably means your baby’s trying to tell you something, but she’s most likely not in distress.

In some cases, tearless crying can be a sign of something more serious, like dehydration. If you notice that your baby’s perpetually dry-eyed, make sure she’s drinking enough fluids. If the problem persists, her tear ducts may be blocked, a condition that should clear up on its own within a few months; your pediatrician may recommend you help it along by gently massaging the inside corners of your baby’s eyes.