Baby Week 23 Development: What to Expect

17 de abril de 2026|Poco Koko Team

Something shifts at twenty-three weeks. Your baby is no longer content to sit and observe — they want to participate. If a toy is out of reach, they lunge for it. If a rattle makes noise when shaken, they shake it again and again, delighted that they caused the sound. Your 23 week old baby is roughly five and a half months old, and this week marks a transition from passive discovery to intentional action. I noticed this change during a Saturday morning floor session when my baby spotted a crinkle book just beyond arm's reach, leaned forward from a seated position with alarming determination, grabbed it with both hands, and immediately shook it to hear the noise. It was the first time I saw her connect "I do something" with "something happens" — and she looked genuinely thrilled about it.

Quick Answer

At 23 weeks, most babies lunge forward from a seated position to grab toys, show stronger core stability during floor play, begin understanding cause-and-effect relationships like shaking a rattle to produce sound, and may show the earliest signs of separation anxiety when a caregiver leaves the room.

What's Happening at Week 23

Gross motor: Your baby's core strength has noticeably improved. Sitting is steadier this week — many 23-week-olds can maintain an upright seated position for longer stretches before tipping. The big development is lunging. Your baby leans forward from sitting, reaches for a toy, and sometimes topples in the process. This lunging motion builds the trunk rotation and weight-shifting skills that eventually lead to crawling. Some babies also begin pushing up onto hands and knees briefly during tummy time, rocking back and forth without going anywhere yet.

Fine motor: Grasping is more deliberate now. Your baby reaches with purpose, adjusts their hand as it approaches an object, and holds items with a firmer grip. They transfer objects between hands more smoothly and bring everything to their mouth for oral exploration — which remains their primary way of learning about texture, shape, and temperature.

Cognitive: Cause-and-effect understanding is the standout development at week 23. Your baby shakes a rattle and hears a sound, then shakes it again to test whether the same thing happens. The AAP identifies this kind of repeated, intentional action as an important cognitive milestone — it shows your baby is forming predictions and testing them. They may also start dropping objects deliberately to watch them fall, which looks like mischief but is actually early scientific thinking.

Language: Babbling expands noticeably at week 23. Your baby produces a wider variety of consonant-vowel combinations — mixing "ba," "da," "ga," and "ma" into longer strings that sound increasingly conversational. They experiment with volume and pitch, sometimes shrieking with excitement during play. This vocal variety is not random noise — it is your baby practicing the rhythm and cadence of real speech.

Social and emotional: Separation anxiety may make its first appearance around this time. Your baby has developed strong attachments and now notices — and protests — when a primary caregiver leaves the room. According to the CDC developmental milestones guidance, this reaction is a healthy sign of secure attachment, not a problem to be solved. Brief separations followed by warm reunions help your baby learn that you always come back.

Best Activities for Week 23

Rattle cause-and-effect play — Offer your baby a lightweight rattle or shaker toy and let them discover the connection between their movement and the sound it produces. When they shake it, narrate what is happening: "You shook it and it made a sound!" Repetition is the point — every shake reinforces the cause-and-effect loop.
Seated reaching challenges — While your baby sits on the floor, place interesting toys just slightly beyond easy arm's reach. This encourages the lunging and leaning that builds core stability and trunk rotation. Stay close enough to catch them if they topple forward.
Drop and watch games — Sit your baby in your lap at a table edge and hand them a soft toy. When they drop it (intentionally or not), pick it up with an exaggerated reaction and hand it back. Babies at this stage can repeat this cycle endlessly because they are learning about object permanence and gravity at the same time.
Peek-a-boo with variations — Classic peek-a-boo directly addresses separation anxiety by teaching your baby that hidden things still exist. Use a cloth to cover your face, then reveal yourself. Vary the timing and direction to keep the surprise element alive. This simple game builds trust and emotional resilience.
Texture exploration on the mat — Gather items with different textures — a wooden spoon, a silk scarf, a rubber teether, a rough washcloth — and let your baby handle each one during floor time. At 23 weeks, they will mouth everything, so ensure all items are clean and safe. This multi-sensory play supports both fine motor development and cognitive growth.

Creating the Right Environment

A 23-week-old who is lunging, toppling, and spending extended time on the floor needs a surface that supports active movement without creating hazards. Hard floors make every forward lunge a face-first collision. Foam tiles shift apart under the force of a lunging baby, creating gaps and instability. Blankets bunch up and slide, turning a simple reach into a tumble.

A PocoKoko memory foam play mat provides the firm, flat cushioning this stage demands. The continuous surface stays put while your baby lunges, rolls, and pushes up onto hands and knees. The non-toxic, CertiPUR-US certified construction means every mouthed toy that touches the mat surface is picking up zero harmful chemicals. When floor time is this active and this frequent, investing in the right surface pays off at every session.

23 week old baby reaching for toy while sitting on PocoKoko memory foam play mat

When to Talk to Your Pediatrician

Babies develop at their own pace, and variation from week to week is normal. However, consult your pediatrician if your 23-week-old does not reach for or show interest in nearby objects, cannot support their head when sitting with assistance, does not turn toward familiar voices, or shows no reaction when you leave or return to the room. The AAP encourages parents to trust their instincts — if something feels off, asking early is always the right call. Early intervention leads to the strongest outcomes.

FAQ

What should a 23 week old baby be doing?
At 23 weeks, most babies sit with improved stability, lunge forward to reach toys, understand basic cause-and-effect like shaking a rattle to make sound, and may begin showing early separation anxiety when a caregiver leaves the room.

Is separation anxiety normal at 23 weeks?
Yes. Early separation anxiety can appear around 23 weeks as babies form stronger attachments to primary caregivers. This is a healthy sign of secure attachment and cognitive development. It typically intensifies between 8 and 12 months before gradually easing.

How can I help my 23 week old develop cause-and-effect understanding?
Offer toys that respond to your baby's actions — rattles that make sound when shaken, crinkle books that make noise when squeezed, or balls that roll when pushed. Let your baby experiment repeatedly without interruption. Narrating what happens reinforces the connection between action and result.