1. CHANGE IN BEHAVIOR :

Wouldn't it be so much easier if babies could tell you what's bothering them? Unfortunately, it's not that simple. But, according to Southern Californina-based pediatrician and pediatric advisor for The Newborn Channel, Tanya Remer Altmann, MD, FAAP, paying attention to your baby's behavior can clue you in. "Sometimes the changes are subtle and sometimes more obvious, but any changes from your baby's normal routine may be a tip-off that something may not be right and that you should call your pediatrician," Altmann said.

2. HIGH TEMPERATURE :

How high is too high when it comes to infant temperatures? Erin Taback, MD, founder of Oak Park Pediatrics in Oak Park, Illinois, advises new parents to call their pediatrician immediately during the newborn period if the baby has a fever of more than 100.4 degrees rectally. "This is considered an emergency," she said.

3. FREQUENT VOMITING :

All of our experts agreed on this reason – if your little one is experiencing frequent vomiting, it's definitely time to call your pediatrician for help.

4. DIFFICULT BREATHING :

Is your newborn experiencing rapid or difficult breathing? If so, Altmann recommends calling your pediatrician immediately. In addition, Lauren Crosby, MD, FAAP, of La Peer Pediatrics in Beverly Hills, California, advises new parents to watch for a cough, especially one that's constant or doesn't allow baby to rest.

5. LACK OF URINATION :

How often is your baby urinating? According to Crosby, if your newborn isn't urinating at least every six hours, you should call your pediatrician.