Newborns can’t tell you when something is wrong, so you have to read their bodies and behavior for clues. The good news: most of the warning signs are visible if you know where to look. A baby who is alert when awake, feeding well, and can be comforted when crying is generally doing fine. It’s when those baseline behaviors shift that you need to pay closer attention.
Fever in the First Two Months
A rectal temperature of 100.4°F (38°C) or higher in a baby under two months old is a medical emergency. At this age, a fever can signal a serious infection that a newborn’s immune system isn’t equipped to fight on its own. Don’t wait to see if it comes down. Head to the emergency department.
On the flip side, a temperature that drops too low can also be a warning sign. If your baby feels cool to the touch and their temperature reads below 97.7°F (36.5°C) even after being bundled, that’s worth a call to your pediatrician. Temperature instability in either direction, running unusually hot or cold, is one of the earliest subtle signs of infection in newborns.
Use a rectal thermometer for the most accurate reading in a newborn. Forehead and armpit readings aren’t reliable enough at this age to rule out a true fever.
Changes in Breathing
Newborns breathe faster than adults, typically 30 to 60 breaths per minute, and it’s normal for their rhythm to be a little irregular. What isn’t normal is visible effort. Three signs stand out:
- Nasal flaring: the nostrils spread wide with each breath, as if the baby is trying to pull in more air.
- Chest retractions: the skin between or below the ribs pulls inward visibly during each breath, creating a sucking-in look.
- Grunting: a short, low sound at the end of each breath, different from the occasional newborn grunt during sleep or a bowel movement. Grunting with every breath means your baby is working hard to keep their lungs open.
Any of these happening consistently, not just for a moment after a sneeze, warrants immediate medical attention. A baby whose skin turns bluish or grayish around the lips, tongue, or fingernails is not getting enough oxygen and needs emergency care right away.
Lethargy vs. Normal Sleepiness
Newborns sleep 16 to 17 hours a day, so “sleeping a lot” by itself isn’t a red flag. The difference between a sleepy baby and a lethargic one comes down to what happens when they’re supposed to be awake.
A lethargic baby sleeps longer than usual, is hard to wake for feedings, and even when awake, doesn’t seem alert or responsive to sounds and faces. They appear to have little energy, almost floppy or sluggish. Compare that to a healthy sleepy baby who, once awake, locks eyes with you, roots for the breast or bottle, and reacts to noise. If your baby won’t wake up enough to feed, or wakes but immediately drifts off without eating, that’s a warning sign worth acting on quickly.
Feeding Problems
How your baby eats is one of the most reliable indicators of how they’re feeling. A sick newborn often loses interest in feeding or can’t sustain it. If a breastfed baby consistently stops feeding after 10 minutes or less, or if a bottle-fed baby repeatedly refuses to latch onto the nipple, something may be off. A baby who seems hungry immediately after feeds, constantly rooting and searching for something to suck, may not be transferring enough milk.
Vomiting is different from normal spit-up. Most newborns spit up small amounts after feedings. Forceful vomiting that shoots out, vomit that looks green or bloody, or vomiting after every single feeding is not normal. A swollen or firm belly that seems tender when touched can also signal a digestive problem.
Wet Diapers and Dehydration
Counting wet diapers is the simplest way to track whether your baby is getting enough fluid. After day five of life, you should see at least six wet diapers in a 24-hour period. Fewer than that suggests your baby may not be taking in enough milk, or may be losing too much fluid through illness.
Beyond diaper counts, dehydration has physical signs you can spot. The soft spot on top of your baby’s head, called the fontanelle, is a built-in hydration gauge. Normally it’s flat or slightly curved. If it looks noticeably sunken, like a shallow dip, that’s a sign of serious dehydration that needs urgent treatment. Other dehydration clues include a dry mouth with no saliva, no tears when crying, and dark or concentrated urine.
Skin Color Changes
Jaundice, a yellowing of the skin and the whites of the eyes, is extremely common in the first week of life and usually harmless. It typically appears within a few days after birth and resolves on its own. You can check for it by pressing gently on your baby’s forehead or nose: if the skin looks yellow where you pressed, mild jaundice is likely present.
Jaundice becomes concerning when it spreads. Yellowing that stays on the face is usually mild. When the yellow color extends to the belly, arms, or legs, bilirubin levels may be getting too high and need to be checked. Jaundice that appears in the first 24 hours of life, deepens quickly, or comes with a baby who is hard to wake and feeding poorly is a different situation from the garden-variety kind.
Other color changes to watch for: a pale or grayish tone to the skin, a mottled or blotchy appearance that doesn’t go away with warming, or any blue tint around the lips or tongue. Newborns commonly have bluish hands and feet in the first day or two, which is harmless, but blue centrally (lips, tongue, torso) is always urgent.
Subtle Signs of Serious Infection
Newborn infections can be sneaky. The symptoms don’t always look like what you’d expect from a “sick” person. Instead of a dramatic fever and obvious distress, a newborn with a developing infection may simply seem “off.” The early warning signs include reduced movements, weaker sucking, temperature swings in either direction, breathing changes, diarrhea or a sudden drop in bowel movements, and a swollen belly.
What makes newborn infections tricky is that no single symptom is definitive. It’s the combination and the change from your baby’s baseline that matters. A baby who was feeding well yesterday and today won’t latch, who was active and is now limp, who had six wet diapers and now has two: that pattern of decline is what to watch for. Trust your instinct when something feels different. Parents who spend all day with their baby often notice changes before they become medically obvious.
What “Normal but Alarming” Looks Like
Some things that look scary in a newborn are actually harmless. Sneezing frequently is normal and helps clear tiny nasal passages. Hiccups happen often and don’t bother babies the way they bother adults. Occasional trembling of the chin or lower lip is part of an immature nervous system and isn’t a seizure. Irregular breathing during sleep, where the baby pauses for a few seconds and then takes several quick breaths, is a normal pattern called periodic breathing.
A true seizure in a newborn looks different from trembling: it involves repetitive, rhythmic jerking that you can’t stop by gently holding the limb, or subtle signs like repetitive eye movements, lip smacking, or sudden stiffening of the whole body. Seizures always need emergency evaluation.
The most practical thing you can do in the first weeks is learn your baby’s normal. How long they typically sleep between feeds, how vigorously they suck, how they sound when breathing, what their skin tone looks like in natural light. Once you know their baseline, any meaningful deviation becomes much easier to spot.