Appearance
Jaundice, Dehydration, Fever, and When to Call
This is one of the highest-stakes pages in the first two weeks because jaundice, dehydration, and infection often overlap. A baby who is not taking in enough milk can become dehydrated; dehydration can worsen jaundice; and a baby with infection may show poor feeding, sleepiness, or temperature change before anything else becomes obvious 123. The practical question is not whether every yellow or sleepy baby is in danger. It is whether the current picture still fits ordinary newborn adjustment.
Jaundice is common, but timing and severity matter
Some jaundice is common in newborns, especially in the first days after birth. What makes clinicians more cautious is jaundice that appears very early, deepens quickly, extends further down the body, or comes with poor feeding or low output 124. Follow-up bilirubin checks are interpreted using the baby's age in hours, not just the number by itself, which is why discharge timing and follow-up timing matter 24.
If the baby looks yellow in the first day of life, or the yellow color is clearly worsening instead of plateauing, that is a same-day call. In a newborn, there is not much upside to waiting and seeing.
Dehydration usually shows up through the feeding-and-output story
Babies do not usually announce dehydration in a dramatic way at first. The clues are often a baby who is harder to wake, feeding poorly, making fewer wet diapers, or seeming drier and less vigorous 134. A family may feel like the baby is feeding constantly, but the body may still be telling a different story through weight loss, output, and worsening jaundice.
Fever in a newborn is different from fever in an older baby
A rectal temperature of 38.0 C / 100.4 F or higher in a baby under 3 months deserves prompt medical evaluation, and in a newborn it should not be watched at home to see what happens 35. Fever is only one concern; some newborns with serious illness present as unusually sleepy, poorly feeding, pale, or floppy rather than clearly hot 35.
What the evidence and current guidance suggest
The 2022 AAP hyperbilirubinemia guidance kept the focus on universal bilirubin assessment before discharge and follow-up based on age in hours and risk factors, while adjusting treatment thresholds to better balance treatment and overtreatment 2. That does not make jaundice casual. It means the best practice is structured follow-up rather than guessing by skin color alone 124. Feeding support remains central because better intake often helps reduce the risk of bilirubin rising further in otherwise typical breastfeeding jaundice 14.
Seek urgent care now if
- rectal temperature is 38.0 C / 100.4 F or higher
- the baby is very hard to wake, limp, or breathing unusually
- urine output is low and feeding is going poorly
- jaundice is clearly worsening or the baby looks yellow down to the legs or soles
- vomiting is persistent or forceful
- the baby simply looks less well than before 1235
Call the same day if
- the yellow color is spreading after the first day instead of fading
- wet diapers are down and the baby is not waking well for feeds
- feeding has become weaker or shorter than it was yesterday
- the baby has a new temperature issue but is otherwise acting okay
- you are unsure whether the baby is actually improving or only changing shape 124
What to have ready when you call
Have the baby's age in days, feeding method, approximate feed frequency, diaper counts, last recorded temperature, discharge timing, and any bilirubin results if you have them. That information helps the clinician decide whether you need office follow-up, lab work, or urgent evaluation 124.