A newborn’s illness or infection are a constant worry for new moms – especially when babies born during cold and flu season. Babies in their first weeks of life are at their highest risk of getting seriously ill because their immune system hasn’t had a chance to fully develop and they’re relying largely on the antibodies passed on by mom at birth.

Here are some helpful tips to remember during those first critical weeks of life.

When to take baby to the ER

Get emergency care if you notice any of the following with your baby:

• Vomit that’s green or bloody
• Dusky or blue skin or lips
• Floppiness or extreme difficulty waking the baby
• Poisoning or suspected poisoning
• Trouble breathing or chest sinking in with breathing

When to Take Baby to the Pediatrician’s Office

Call your baby’s doctor if you notice any of the following:

Signs of infection or illness

All newborn babies sleep a lot but if you notice your baby becoming listless or sleeping excessively, she may be getting sick.  Be watching for additional signs of illness like an abnormal temperature — a baby’s normal temperature is from 97.7 to 99.5 degrees Fahrenheit – poor eating, reddened or firm skin around the umbilical cord, and excessive irritability.

Skin conditions

Your baby’s doctor will want to hear from you if your baby begins to develop jaundice (a yellow appearance) that doesn’t go away or spreads to other parts of the body. Other skin conditions that may be worth a call to your doctor include a rash that concerns you, mottled and pale skin with a temperature that’s higher or lower than normal, cradle cap, or severe diaper rash.

RELATED: What Your Baby's Skin Is Telling You

Bowel movements and wet diapers

Pay attention to the number of wet and messy diapers your newborn makes. Too few, or sudden changes in bowel movements, may signal a problem.

Remember: You know your baby best. If you feel something is very wrong with your infant, call your doctor or bring your child to the emergency room.