This Childhood

3–6 months: what changes for your baby

Quick answer

Between three and six months, FOUNDATION says your baby starts to join in: looking, reaching, laughing and making sounds. The chapter's focus is back-and-forth talk, plenty of floor time, a gentle day-night rhythm, acting early on any developmental concern, and getting ready for solids, iron and allergens without starting before four months.

What changes for your baby at 3–6 months?

Chapter 3, The world gets interesting, asks you to follow what catches your baby's interest rather than a schedule of activities, and to give him or her room to move and to talk.

Talk with your baby, not just near your baby. The book describes parentese as a voice just for your baby: higher, slower and sing-song, with or without made-up baby words. It cites a randomized trial in which coaching parents from six months increased back-and-forth talk and improved language at eighteen months; the coached parents took more turns rather than simply talking more. By about six months many babies laugh, squeal and blow raspberries, so copy the sound back and see how long the exchange lasts. A screen or speaker can't answer in the moment; video calls with a grandparent or an absent parent are the exception, and the book notes that pediatricians advise against cartoons and nursery-rhyme videos for babies this young.

Give movement some space. Mix supervised tummy time (by now, at least 15 to 30 minutes a day in total) with back play, reaching and supported positions, with a safe toy placed just within reach. Keep swings, bouncy seats and car seats outside the car to short spells. Never step away from a changing table, even for a moment. If your baby was born early, the book says to check milestones by corrected age for the first two years.

What should you prepare for at 3–6 months?

A rhythm, gently. Make days bright and sociable and nights dim and quiet, and let a short routine of feed, change, song and safe sleep become familiar without a rigid timetable. Stop swaddling as soon as your baby looks ready to roll, and lower the crib mattress before he or she can sit up. On how much sleep to expect, the book says:

For babies four to twelve months old, sleep specialists recommend 12 to 16 hours of sleep per 24 hours, naps included.

It calls that a guide, not something to force. Raise persistent snoring, labored breathing or extreme daytime sleepiness with your baby's clinician, and "Call 911 if your baby is struggling to breathe at any time".

A developmental concern, acted on. Bring examples, or a phone video if the thing you've noticed comes and goes, and ask whether a developmental screen or fuller evaluation is needed. A lost skill should be checked promptly. For a child under three you can also contact your state's early intervention program directly, while also asking your clinician for a referral.

You don’t have to wait for a medical diagnosis or a doctor’s referral to ask for this public evaluation, and the evaluation is free.

First foods, iron and allergens: plan, don't rush. Readiness is visible: good head control, sitting upright with support, and swallowing food instead of pushing it out. For a breastfed or partly breastfed baby, the four-month visit is the time to discuss an iron supplement; a baby born early needs a separate plan.

Ask at the four-month visit: “What is our iron plan from now until solids are established, and when will we review it?”

Once your baby is ready, the book advises against deliberately delaying the common allergens; the prevention evidence is strongest for peanut and cooked egg. With severe eczema or an egg allergy, raise peanut at the two- or four-month checkup.

Questions parents ask

Can my baby start solids at four months?

Not before. The chapter says:

Don't begin before four months. Most babies start around six months.

Should I add cereal to the bottle to help my baby sleep longer?

No. "Night waking can still be normal." The book adds:

Don't hold back feeds your baby needs, and don't add cereal to bottles to make sleep longer.

Nor, the book says, do early solids help a baby sleep through the night.

Are baby walkers bad?

The book's answer is direct: "Don't use a seated infant walker with wheels." It can cause serious injury and doesn't help a baby learn to walk. Use a play yard when you need your hands free.

Sources

Selected from the source notes the book lists for this chapter and matched to the guidance above. The book treats its source notes as a reading guide, not proof of every sentence, and listing a source does not mean that organization has reviewed or vouched for FOUNDATION.

← 0–3 months · All stages

FOUNDATION by THIS CHILDHOOD is a personalized digital parenting book, delivered as a PDF and an EPUB, that runs from before birth to 18. About the book

A note from the book

This guide assumes a generally healthy, full-term child, and it’s general education, not medical care tailored to yours.

Prematurity, growth concerns, a disability, illness, allergy, a feeding difficulty or medication can change that plan. If one applies, the book says to ask your child's pediatrician or specialist what changes for your child. It also says research hasn't found a parenting formula that guarantees a particular outcome.

This book has not had independent clinical review.

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