Your Newborn's Health: Screenings, Common Worries, and the One Fever Rule

In one minute

• Newborn screening (heel-stick blood test, hearing check) happens automatically in the first days — you don't need to arrange it.
• Jaundice shows up in about 6 in 10 babies, usually peaks around day 2–3, and typically fades within two weeks.
• Frequent spit-up (reflux) is normal — it affects most babies at 1 month and usually doesn't need treatment.
• Any rectal temperature of 100.4°F (38°C) or higher before 3 months is an emergency, full stop.

The screenings happening behind the scenes

Before you leave the hospital, baby gets a heel-stick blood test screening for 45+ metabolic and genetic conditions, plus a hearing check. If the hearing screen doesn't come back clear, it just means a repeat test by 3 months — it doesn't mean there's a problem, only that it needs a second look. These systems exist precisely so serious but treatable conditions get caught early, often before you'd ever notice a symptom.

Jaundice and spit-up: common, usually fine

Jaundice — that yellowish tint to skin and eyes — affects roughly 6 in 10 newborns, usually peaks around day 2–3, and resolves within about two weeks for most term babies. It's checked at routine visits and treated with phototherapy if levels get high enough, a well-established, low-risk treatment. Spit-up is its own kind of common: about 7 in 10 one-month-olds bring up milk at least once a day, and it typically peaks around 3 months before easing off entirely by a year. In healthy, thriving babies, it almost never needs medication.

The one rule with no exceptions: fever

A newborn's immune system is still learning the job, so fever gets treated differently than at any other age. Any rectal temperature of 100.4°F (38°C) or higher in a baby under 3 months needs same-day medical evaluation — not a wait-and-see, not a dose of infant Tylenol first. It sounds strict because it is: about 1 in 10 febrile young babies turns out to have a urinary tract infection, and doctors would rather check and rule things out than miss something.

When to call your pediatrician: any fever ≥100.4°F/38°C under 3 months (go straight to urgent care or the ER); jaundice appearing in the first 24 hours or spreading to palms and soles; jaundice still present after about 2 weeks (3 weeks if baby was premature), or pale/chalky stools and dark urine at any point — these need a same-week check, not a wait-and-see; fast or labored breathing; extreme sleepiness or trouble waking; or vomiting that's forceful or happens after every feed.

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Go deeper: Crying, colic & the PURPLE crying curve

Sources

1. NHS (2025). Jaundice in Babies. https://www.nhs.uk/conditions/jaundice-in-babies/
2. PMC/NCBI (2019). Natural history of gastroesophageal reflux in infancy: new data from a prospective cohort. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7137340/
3. Mayo Clinic (2024). Fever in Newborns. https://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/healthy-baby/art-20047793