What to Look For
When your baby seems unwell, you need a clear next step. Start here, and call your care team whenever you are worried.
Original guidance checked July 2026 · See the linked sources for updates
- The number: 100.4 °F rectal, under 3 months = call right away.
- Blue lips, hard breathing, a rash that won't fade when pressed, floppy: 911.
- Most scary-looking newborn things are normal. The table below sorts them.
- Unsure? Call. That is what the office is there for.
The one number: 100.4
A fever is a rectal temperature of 100.4 °F (38 °C) or higher — that's the American Academy of Pediatrics' own line. source
A rectal digital thermometer gives the reading that counts at this age. Forehead and ear readings are fine for screening later, but under 3 months, rectal is the standard. Never a mercury thermometer. source
3–6 months: any fever is worth a call within 24 hours. Any age: call right away for fever repeatedly above 104 °F, fever with a stiff neck, unexplained rash, trouble breathing, unusual drowsiness, or fever lasting more than 24 hours in a child under 2. source source
Call 911. Now.
From the AAP's own emergency list: source
- Difficulty breathing; skin or lips that look blue, purple, or gray
- Unresponsive, unconscious, or decreasing responsiveness
- Seizure: rhythmic jerking with loss of responsiveness
- Rapidly spreading purple or red rash, especially tiny dots that don't fade when pressed, with fever source
- Vomiting blood; bleeding that won't stop
- Severe dehydration: sunken eyes, no tears, no urine, floppy and lethargic
Call the pediatrician now (same day, any hour)
- Working to breathe: fast breathing, nostrils flaring, head bobbing, rhythmic grunting, skin tugging between ribs or at the base of the neck, pauses over 10 seconds. source
- Dehydration: under 6 wet diapers a day in an infant, dry mouth, few tears, sunken soft spot. source
- Vomiting that means business: green (bile) vomit, coffee-ground appearance, forceful vomiting after every feed (in the first weeks this pattern can be pyloric stenosis), vomiting beyond 24 hours, or a swollen belly. source
- Jaundice spreading or deepening: yellow reaching the belly, arms, or legs; yellow eye-whites; baby hard to wake or feeding poorly. source
- Behavior change: floppy, unusually drowsy, inconsolable for hours, or just profoundly "off." Trust that instinct.
- Umbilical cord: foul-smelling discharge, spreading redness at the base, or active bleeding. source
Looks alarming, is normal
| Thing | The reassuring facts |
|---|---|
| Red blotchy rash, days 2–3 | Erythema toxicum: over half of newborns get it; gone in 1–2 weeks, no treatment. source |
| Baby acne / tiny white bumps | Acne in 30%+ of newborns from week 2–4; milia in 40% at birth. Both self-resolve. source |
| Yellow scales on the scalp | Cradle cap: 70% of 3-month-olds; not itchy, not contagious, goes away. source |
| Pause-y, irregular breathing | Periodic breathing: pauses under 10 seconds are normal newborn wiring. (Over 10 seconds or turning blue: call.) source |
| Sneezing, hiccups, chin trembles | Standard equipment. Sneezing clears dust (no cold required); hiccups are harmless. source |
| Occasionally crossed eyes | Normal in early months while eye muscles coordinate; constant crossing, or any regular crossing after 4 months, gets checked. source |
| Flailing "startle" with crying | The Moro reflex: arms fling out, then clutch in. Peaks month 1, fades by ~2–4 months. source |
| Swollen genitals or breasts; a little vaginal discharge or even blood | Your hormones, temporarily on loan. Resolves over the first weeks. source |
| Evening fuss-and-feed marathons | Cluster feeding + witching hour. Normal, exhausting, temporary. source |
Milestones, and when to act early
The CDC's checklists (revised 2022) list what 75% or more of babies do by each age, so a missed milestone is a real signal rather than a borderline call. The free CDC Milestone Tracker app makes this easy. source
| By… | Most babies… |
|---|---|
| 2 mo | Smile at you, calm when spoken to, watch your face, make non-crying sounds, hold head up in tummy time. source |
| 4 mo | Smile to get attention, chuckle, coo, hold head steady, bring hands to mouth, push up on forearms. source |
| 6 mo | Know familiar people, laugh, take turns making sounds, reach for toys, roll tummy-to-back, lean on hands sitting. source |
| 9 mo | Respond to their name, react to peek-a-boo, babble "mamamama," sit without support, pass things hand to hand. source |
| 12 mo | Wave bye-bye, call a parent mama/dada, play pat-a-cake, pull to stand, cruise furniture, pincer-grasp small bits. source |
Act early if your baby misses a milestone, loses any skill they had, or you're simply concerned: say so at the next visit (or call before it), and ask about a developmental screening. Early help works best early. The CDC's slogan is literally "Don't wait." source
Warning signs in you
Up to a year after delivery, these are seek-care-immediately signs, from the CDC's Hear Her campaign: heavy bleeding (soaking a pad in an hour), a headache that won't quit or gets worse, vision changes, fever of 100.4+, chest pain or racing heart, trouble breathing, severe belly pain, one-sided leg swelling or pain, extreme swelling of hands or face, and thoughts of harming yourself or your baby. source
The emotional side (baby blues vs. postpartum depression and anxiety, in birthing parents and dads) has its own full guide: Your Wellbeing. If you need someone right now: call or text 988, or the National Maternal Mental Health Hotline at 1-833-852-6262 (free, confidential, 24/7). source
About the sources on this page
- The American Academy of Pediatrics (AAP)
- The professional organization of America's pediatricians. Its guidance on safe sleep, fevers, feeding, and screen time is what your own pediatrician is trained to follow; its parent site is HealthyChildren.org.
- The Centers for Disease Control and Prevention (CDC)
- The U.S. government's public-health agency. It sets the childhood vaccine schedule and publishes the developmental-milestone checklists.
- The U.S. Department of Agriculture (USDA)
- The federal agency behind the official Dietary Guidelines, which include infant and toddler feeding.
- MedlinePlus
- The plain-language medical encyclopedia run by the National Institutes of Health, the U.S. government's medical-research agency.
Written by J. Ladis and Haley Dell, who are parents, not doctors. This is general education for healthy, full-term babies, not medical advice. Your pediatrician and OB know your family. When this page and your doctor differ, your doctor wins. Premature babies and babies with health conditions often have different rules.
Facts checked against the linked sources, July 2026.