Infants at 4 Months: Milestones, Sleep, Weight and Checkup
What a 4-month-old typically does, weighs and sleeps, from MedlinePlus and the AAP, plus what the 4-month checkup covers and which skills usually arrive next.
The newborn who only ate, slept and cried has started laughing at you, grabbing the rattle and refusing to keep their head down, and you want to know whether all of that is on schedule. Two sources set out what a 4-month-old typically does: the MedlinePlus milestones record, which is the National Library of Medicine’s encyclopedia, and the American Academy of Pediatrics’ HealthyChildren pages. Here is what they list, side by side, with MedlinePlus’s own caution up front: “All children develop a little differently. If you are concerned about your child’s development, talk to your child’s health care provider.”
The quick answer
| Area | Typical at 4 months, as the sources put it |
|---|---|
| Head and trunk | “Have almost no head droop while in a sitting position”; “Raise their head 90 degrees when placed on their stomach”; holds head steady without support when you hold them |
| Movement | “Be able to roll from front to back”; pushes up on elbows and forearms on tummy; uses arms to swing at toys |
| Hands | “Hold and let go of an object”; “Be able to grasp a rattle with both hands”; brings hands to mouth; cannot yet pick a dropped rattle back up |
| Sounds | “Be able to coo”; “Be able to laugh out loud” (MedlinePlus); “Chuckles (not yet a full laugh)” (AAP); makes sounds back when you talk |
| Seeing and attention | Visual range “increased to several yards or more”; “Increase eye contact”; “Begin to show memory”; “Demand attention by fussing” |
| Weight | Weight gain slows “to about 20 grams (almost two thirds of an ounce) per day”; typically “2 times more than their birth weight” |
| Sleep | “Sleep 9 to 10 hours at night with 2 naps during the day (total of 14 to 16 hours per day)” |
Movement: the head, the roll and the hands
MedlinePlus lists the physical skills a typical 4-month-old “should” have: almost no head droop when sitting, able to “sit straight if propped up”, able to raise the head 90 degrees on the stomach, able to “roll from front to back”, able to “hold and let go of an object”, to “play with a rattle when it’s placed in their hands, but won’t be able to pick it up if dropped”, to “grasp a rattle with both hands”, and to “place objects in the mouth”.
The AAP’s list for the same age is shorter and worded as what you will see: “Holds head steady without support when you are holding them”, “Holds a toy when you put it in their hand”, “Uses their arms to swing at toys”, “Brings hands to mouth”, and “Pushes up on elbows/forearms when on tummy”. Rolling front to back is on the MedlinePlus list but not the AAP’s 4-month list, so treat it as something that may or may not have arrived. Rolling the other way, back to stomach, is on the MedlinePlus 6-month record with “by 7 months” beside it.
Sounds and attention
Both sources describe the same shift from reacting to initiating. MedlinePlus: “Be able to coo”, “Be able to laugh out loud”, “Increase eye contact with parents and others”, “Begin to show memory”, “Demand attention by fussing”, “Recognize parent’s voice or touch”, and “Anticipate feeding when able to see a bottle (if bottle-fed)”. The AAP: “Makes sounds like ‘oooo,’ ‘aahh’ (cooing)”, “Makes sounds back when you talk to them”, “Turns head toward the sound of your voice”, “Smiles on their own to get your attention”, “Chuckles (not yet a full laugh) when you try to make them laugh”, and “Looks at their hands with interest”.
The two sources differ on one word: MedlinePlus expects a laugh out loud, the AAP describes a chuckle “not yet a full laugh”. Either is within the range they describe.
On sight, the AAP says the 4-month-old’s “visual range has increased to several yards or more”, that they “may be more interested in circular patterns”, and that they respond “to the full range of colors and their many shades”.
Weight and sleep numbers
MedlinePlus is the source that puts numbers on this age. Weight gain slows “to about 20 grams (almost two thirds of an ounce) per day or 1 and a third pounds (600 grams) per month”, and the typical 4-month-old weighs “2 times more than their birth weight”. The 6-month record adds the other side of that: birth weight “often doubles by 4 months, and it would be cause for concern if this hasn’t happened by 6 months”.
Sleep: “9 to 10 hours at night with 2 naps during the day (total of 14 to 16 hours per day)”. If the nights have just fallen apart, that is a known pattern at this age; see 4-month sleep regression and how to get through it and, for the ages after it, sleep regression ages: what to expect.
What the 4-month checkup covers
The AAP’s checkup checklist for 4 months says the visit includes measuring and weighing, observing development and behaviour, and a physical exam, and that the baby “may receive the second doses” of five vaccines: rotavirus, DTaP, Hib, PCV and IPV. Two screenings are listed: the pediatrician “will ask you how you are feeling” about postpartum depression, and a hematocrit or hemoglobin test for babies born preterm or with low birth weight.
Among the questions the pediatrician may ask, one carries a number: “If you are breastfeeding, are you giving your baby an iron supplement? (The AAP recommends giving breastfed infants 1 mg/kg/day of a liquid iron supplement until iron-containing solid foods are introduced at about six months of age).” The safety questions are about where the baby sleeps, the rear-facing car seat, and a water heater set so the faucet is “at or below 120 degrees Fahrenheit”. If you tend to leave the appointment having forgotten what you meant to ask, questions parents should ask pediatricians but might forget is a list to take in.
Play that fits this age
MedlinePlus’s suggestions: “Place the baby in front of a mirror”, “Provide bright-colored toys to hold”, “Repeat sounds the infant makes”, “Help the infant roll over”, tummy time, and one prohibition, “Avoid television and other screen time until age 2 years.” The AAP’s toy list for 4 months is specific: “See-through rattles that show the pieces making noise”, “Cloth books with colorful pictures”, “Unbreakable plastic or mylar mirror”, “Soft balls, including some that make soft, pleasant sounds”, and “Textured toys that make sounds”. Its “did you know” on the checkup page: “It is never too early to start reading with your baby.”
What comes next
The MedlinePlus 6-month record lists what typically arrives between now and then: transferring objects from one hand to the other, picking up a dropped object, rolling from back to stomach, sitting in a high chair with a straight back, the beginning of teething and increased drooling, sounds “resembling one-syllable words (example: da-da, ba-ba)”, and beginning “to fear strangers”. On that list too: the baby “should be able to sleep 6 to 8 hour stretches at night”.
Before you compare your baby to a list
- Both sources say development varies, and both say the same thing to do about a worry: talk to the child’s health care provider or pediatrician.
- Two lists, one age, some differences. Where MedlinePlus and the AAP word a milestone differently, both versions are given above rather than a blend.
- The numbers are typical figures, not thresholds. The only “cause for concern” line either source gives is birth weight not doubling by 6 months.
- Preterm or low birth weight changes the checkup. The AAP checkup page says a baby born preterm or with a low birth weight “may receive this blood screening that helps detect anemia” at 4 months.
More on this year is under babies.
Sources
Milestones, weight and sleep figures are quoted from the MedlinePlus “Developmental milestones record” pages for 4 months and 6 months (National Library of Medicine) and from HealthyChildren.org’s “Developmental Milestones: 1-4 Months Old” and “Checkup Checklist: 4 Months Old” (American Academy of Pediatrics), all read on 21 September 2026.
Frequently asked questions
What should a 4-month-old be able to do?
MedlinePlus lists: almost no head droop when sitting, raising the head 90 degrees on the stomach, rolling from front to back, holding and letting go of an object, grasping a rattle with both hands, cooing and laughing out loud. The AAP's list adds pushing up on the forearms and swinging arms at toys.
How much should a 4-month-old sleep?
MedlinePlus gives 9 to 10 hours at night with 2 daytime naps, a total of 14 to 16 hours a day. The 6-month record says a baby should be able to sleep 6 to 8 hour stretches at night.
How much should a 4-month-old weigh?
MedlinePlus says a typical 4-month-old weighs twice their birth weight and gains about 20 grams a day, roughly 600 grams a month. Its 6-month record adds that birth weight often doubles by 4 months and not doubling by 6 months would be cause for concern.
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