When should I take my newborn to the emergency room versus waiting for a doctor's appointment?

Go to the ER immediately if your newborn (under 3 months) has a rectal temperature of 100.4°F (38°C) or higher, has difficulty breathing, is unusually lethargic or difficult to wake, refuses to eat for multiple feedings, has a blue tint to lips or skin, or has projectile vomiting. For fever in a newborn under 3 months, never wait — this requires urgent evaluation. For non-emergency concerns (mild rash, congestion, fussiness), call your pediatrician's nurse line first. Always err on the side of caution with very young babies.