Week 18 old
Week 18 (about 4 months old): your baby is more alert, laughing, and may be eyeing your food. Here's what's typical for feeding, sleep, and development right now.
In short
At 18 weeks, most babies take about 24-36 oz of breast milk or formula a day across 5-6 feeds and sleep roughly 14-16 hours total, often with longer night stretches and 3-4 daytime naps.
🍼 Feeding
About 24-36 oz of breast milk or formula per day, typically across 5-6 feeds. Breastfed babies usually nurse every 3-4 hours; formula-fed babies often take 4-6 oz per bottle. Most babies are not ready for solids yet — the AAP recommends waiting until around 6 months and signs of readiness like good head control and sitting with support.
😴 Sleep
Roughly 14-16 hours total: about 9-11 hours at night (often with one or two wakeups) and 3-4 naps. Wake windows are usually about 1.5-2.5 hours. Always place your baby on their back to sleep on a firm, flat surface with no pillows, blankets, or bumpers.
What's happening this week
- •Around this age, many babies hold their head steady, push up on their forearms during tummy time, and may start rolling from tummy to back.
- •Lots of babies this age laugh out loud, coo, and 'talk' back when you speak to them.
- •Many are reaching for and grabbing toys, then bringing hands and objects to their mouth to explore.
- •Around now, some families notice fussier sleep and frequent waking, often called the '4-month sleep regression' — it's a normal developmental shift, not a problem to fix.
Milestones to keep in mind
- ✓By the 4-month checkup, many babies smile to get your attention, coo, and turn toward voices — these are ranges, and babies arrive at them on their own timelines.
- ✓Around this age, many babies can hold their head steady without support and bring hands together.
- ✓Babies often push up on their elbows during tummy time and may begin rolling — not every baby rolls by 4 months, and that alone is usually nothing to worry about.
- ✓Mention any milestone questions at the 4-month visit; your pediatrician tracks these as ranges, not weekly checkpoints.
Growth
💡 Tip for this week
If nights got rougher this week, hold your safe-sleep and bedtime routine steady rather than starting new habits — the 4-month sleep shift usually settles, and consistency helps more than quick fixes.
⚠️ When to call your pediatrician
Call your pediatrician for fewer than 4-6 wet diapers a day, a fever of 100.4°F (38°C) or higher, poor feeding or no weight gain, no social smiles, not following objects with the eyes, very stiff or very floppy muscle tone, or if your baby can't hold their head steady at all by the 4-month visit.
Frequently asked
How much should an 18-week-old eat?
Most babies this age take about 24-36 oz of breast milk or formula a day across 5-6 feeds — roughly 4-6 oz per bottle for formula-fed babies, or nursing every 3-4 hours. Solids generally aren't recommended until around 6 months.
Is the 4-month sleep regression happening now?
It can. Around 18 weeks many babies wake more and nap less as their sleep matures — it's a normal developmental phase. Keep a consistent, safe-sleep routine; it usually settles within a few weeks. Talk to your pediatrician if you're concerned.
Can I start solid foods at 18 weeks?
Usually not yet. The AAP recommends starting solids around 6 months, once a baby shows readiness signs like steady head control and sitting with support. Ask your pediatrician before introducing any solids early.
Looking for the bigger picture? See the month 5 overview →
General guidance, not medical advice. Every baby develops at their own pace — talk to your pediatrician with any concerns.