Key checklist for this stage
- At 4 months in Korea: dose 2 of DTaP, polio, Hib, pneumococcal, and rotavirus.
- At 6 months: dose 3 of DTaP, Hib, and pneumococcal, hepatitis B dose 3, and check the timing for polio dose 3 (6–18 months).
- From 6 months, babies are eligible for a flu vaccine every year. In the first year, two doses are given.
- Get the second infant health checkup (4–6 months in Korea).
- Start solids around 6 months, watching for your baby's readiness signs.
- Once the baby starts rolling, never leave them alone on a changing table, bed, or sofa.
Development
Around 4 months, babies hold their head steady and push up on their arms when on their tummy. Rolling from tummy to back usually comes first, and by about 6 months many babies roll. Some start sitting with support.
They reach for and grab toys and bring everything to their mouth. They laugh out loud, babble sounds like 'ba' and 'ma', and turn toward names and voices. They recognize familiar people and are happy to see them.
Feeding and starting solids
The World Health Organization (WHO) recommends exclusive breastfeeding for the first 6 months, and pediatric societies in Korea and abroad advise against starting solids before 4 months. Most babies start around 6 months, based on readiness signs.
It is important to include iron-rich foods early, because the iron stores babies are born with run low around 6 months. Start with a grain porridge, add meat early, and introduce new foods one at a time a few days apart to watch for reactions. There is no need to delay common allergy foods on purpose, but babies with severe eczema or known allergies should see a pediatrician first.
- Readiness signs: good head control, sits with support, shows interest in food, no longer pushes the spoon out with the tongue
- Do not give honey before 12 months (risk of infant botulism).
- Breast milk or formula remains the main source of nutrition after solids start.
Sleep
More babies sleep longer at night, and naps are usually two or three a day. But depending on growth and temperament, many still wake often. A consistent bedtime routine (bath, feed, book, lights out) helps.
Stop swaddling once the baby starts rolling. Keep putting them down on their back, but once they can roll both ways on their own, you do not need to turn them back if they roll during sleep. Still keep pillows, blankets, and toys out of the sleep space.
Health, vaccines, checkups, teeth
In Korea, the second infant health checkup is at 4–6 months. Along with growth measurements, it includes advice on development, feeding, solids, and sleep. Check your baby's vaccine dates on the KDCA immunization helper service. Rotavirus is given as two or three doses depending on the vaccine.
The first tooth usually appears around 6 months, starting with the lower front teeth, but some babies get them earlier and some not until around their first birthday. Once teeth appear, clean them with a soft brush or gauze, using a rice-grain smear of fluoride toothpaste.
Safety
- Once rolling starts, do not leave the baby alone on an adult bed, sofa, or changing table even for a moment.
- Everything goes in the mouth, so keep coins, button batteries, magnets, and small toy parts out of reach.
- The American Academy of Pediatrics (AAP) advises against baby walkers because of falls and tumbles down stairs.
- Do not hold the baby while holding a hot drink.
- Keep the car seat rear-facing.
Play and connection
- Answer your baby's babbling and name the things around you.
- Look at picture books together, pointing to pictures and talking about them.
- Give more tummy time and floor play to practice rolling and crawling.
- Laugh together with mirror play and peekaboo.
Vaccines & checkups in this stage
- General checkup 2 — Age 4–6 months
Korea's Childhood Vaccine Schedule → Infant and Child Health Checkups →
FAQ
When should we start solids?
Most babies start around 6 months, when they hold their head well, sit with support, and show interest in food. Do not start before 4 months. Decide the timing with your pediatrician based on your baby.
My baby is not rolling yet. Is that late?
The age of rolling varies a lot. Give more tummy time, and if after 6 months there are no attempts to roll, or the baby seems very stiff or floppy, discuss it at a checkup.
Which vaccines are given at 6 months?
Under Korea's national schedule, dose 3 of DTaP, Hib, and pneumococcal and hepatitis B dose 3; polio dose 3 is given between 6 and 18 months. Flu vaccine eligibility also starts at 6 months.
Can I use toothpaste once teeth come in?
Once the first tooth appears, brush twice a day with a rice-grain smear of fluoride toothpaste. That amount is fine if swallowed.
My baby wakes often at night. Should we do sleep training?
Night waking is common at this age. Start with a consistent bedtime routine and shape sleep habits gradually to suit your family. If the baby is not feeding well or seems unwell, see a doctor.
Sources
- KDCA immunization helper service (Korea)
- National Health Insurance Service infant health checkups (Korea)
- Korean Pediatric Society
- WHO infant and young child feeding recommendations
- AAP HealthyChildren.org
Medical information is for reference only. This is general information and does not replace diagnosis or treatment. Always talk to your child's doctor. In an emergency in Korea, call 119.
Related
This is when babies start to look into your eyes and smile back. It is also the time of the most crying, so learning how to get through it together matters.
7–9 mo7–9 monthsBabies sit on their own, crawl, and become wary of strangers. As they explore, hazards at home multiply quickly, so safety checks matter most.
Starting solids and toddler foodSolid food fills nutritional gaps and is also how babies learn new tastes, textures and how to feed themselves. Follow your baby's readiness and pace rather than a fixed chart.
Korea's Childhood Vaccine ScheduleIn Korea, national vaccines are free at public health centers and designated clinics. Plan ahead using the standard schedule, and check exact dates and your child's record on the KDCA Immunization Helper.
Infant and Child Health CheckupsIn Korea, infant and child health checkups are national screenings paid for by the National Health Insurance Service (NHIS). Each round has a fixed window, so check the dates and book ahead.
Teeth and Oral CareBrushing starts the day the first tooth appears. A rice-grain smear of fluoride toothpaste, no bottle in bed, and a first dental visit around the first birthday are the basics of cavity prevention.
Sleep and safe sleepWith baby sleep, how safely comes before how long. Set up a safe sleep space first, then support sleep with age-appropriate expectations and a steady routine.