Four months old, often the peak of the sleep change, and frequently another vaccination round. A challenging but very interactive week. Here is what is normal.
Typical day · week 16
- Feeds: 6 to 8 milk feeds in 24 hours
- Sleep: 14 to 16 hours across day and night
- Naps: 3 to 4 naps, wake windows of 1.5 to 2 hours
- Diapers: 5 to 6 or more wet per day
Feeding
Feeding is settled, breast or bottle. It is common to start wondering about solid food around now, but the readiness signs, sitting steadily with support, losing the tongue-thrust reflex, and showing real interest in food, usually arrive closer to six months, which is the recommended starting point. Until then, milk feeds are all your baby needs.
Sleep
For many families weeks sixteen to twenty are the hardest stretch for sleep since the newborn period, as the four-month sleep change peaks and may coincide with post-vaccination unsettledness. Lowered expectations and practical support are the most useful tools, and it does pass. Keep the crib clear and use a sleeping bag now that rolling may have started.
Diapers
Steady output, varying by baby and feeding type, with soft stools the reassuring sign.
Growth
Motor development is strong: your baby may be rolling, pushing up firmly on the forearms, and happily bearing weight on their legs when held standing, which is safe and does not bow the legs. Weight, length and head circumference are tracked on the growth curve at the four-month check.
This week's leap
Four months old brings genuine humor, your baby laughs at things they find funny, the beginnings of object permanence that make peek-a-boo thrilling, and clear likes and dislikes. A vaccination round often falls around four months, with the schedule varying by country; the meningitis B component can again bring a higher fever, so infant acetaminophen as advised helps.
After the meningitis B shot, a temperature above 102.2°F (39°C), a seizure, a pale and floppy baby, or a non-blanching rash needs urgent care. Outside of shots, from three months a fever of 101.3°F (38.5°C) or above warrants assessment. Once rolling starts, a clear, empty crib with a firm, flat mattress and no loose bedding or bumpers is the safe sleep environment. None of this is medical advice; every baby is different, and your midwife, health visitor or doctor is the person to ask about your own child.
The calm way to follow all of this is to log it in one tap as it happens, then read the pattern over a few days rather than carrying it in your head. Little Bean shows this same week-by-week guidance inside the app, beside your own baby's log.
Quick answers: 16 weeks
How often should a 16-week-old eat?
Most babies this age take 6 to 8 milk feeds in 24 hours. Feed on demand rather than by the clock; steady weight gain and enough wet diapers are the real signs intake is fine.
How much sleep does a 16-week-old need?
Roughly 14 to 16 hours across day and night. 3 to 4 naps, wake windows of 1.5 to 2 hours. The range is wide, so treat these as averages rather than targets.
What are typical wake windows at 16 weeks?
3 to 4 naps, wake windows of 1.5 to 2 hours. An overtired baby fights sleep harder, so watch the clock and the tired signs together.
Milestone reference: CDC developmental milestones, 4 months checklist.
One short note, once a month.
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