4-month-old baby: Development, milestones and growth

Nikki Stevenson

Nikki Stevenson

Nikki is a parenting writer and a mom to three wild boys who keep her on her toes (and occasionally make her question her sanity). With over 15 years of experience in the parenting industry, she has more tips and tricks than Mary Poppins on speed dial. When she's not typing away at her keyboard, you can find her sipping on coffee, hiding in the bathroom for five minutes of...
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Updated on Jul 01, 2024 · 11 mins read
4-month-old baby: Development, milestones and growth

Can you believe it's been four months since your little one made their grand entrance into the world?

Time flies when you’re changing nappies and soaking in those precious baby giggles. As you navigate the beautiful chaos of parenthood, your baby is growing in ways you couldn’t have imagined.

From their first adorable attempts at rolling over to those heart-melting moments of recognition, every day with your 4-month-old brings new joys and challenges.

4-month-old baby physical and cognitive milestones

As your baby approaches the four-month mark, you’ll witness a whirlwind of growth and development. Here’s a glimpse into the milestones your little one may reach.

Improved head control
Your baby’s neck muscles are strengthening, allowing them to hold their head up steadily when supported in a sitting position (with their back nearly straight).

Increased muscle strength
Your baby may start to push up on their arms when lying on their stomach, indicating improved muscle tone and strength.

Rolling over
Some babies may begin to roll from their stomach to their back or vice versa, although this milestone can vary widely among infants.

Grasping objects
Your 4-month-old may show an increased interest in reaching for and grasping objects nearby, demonstrating improved hand-eye coordination. This is one of those physical development milestones that make playtime really fun – but be mindful of your baby placing any objects in their mouth. 

Social smiles
Genuine, spontaneous smiles become more frequent, particularly in response to interactions with familiar caregivers and loved ones. They may start mimicking facial expressions. 

Your 4-month-old may start experimenting with different sounds. Gurgling, squealing, laughing, and chuckling might all take place.


Increased alertness
Your baby’s development includes a growing awareness of their surroundings, with longer periods of alertness and engagement during waking hours.

An overview of your baby's growth

Your little one is now a 4-month-old, and what a journey it’s been. Those chubby cheeks and adorable rolls are becoming more prominent with each passing day, a sure sign of their healthy growth. Their tiny fingers and toes are starting to take shape, a testament to the incredible changes happening within their body. 

Internally, their organs are maturing, and their bones are strengthening to support their expanding frame. It’s incredible to witness how rapidly your baby is growing and evolving.

Your 4-month-old's weight and length

At 4 months old, your baby’s growth continues at a steady pace, with both weight and length increasing noticeably. Their birth weight has likely doubled by this point, On average, babies at this age gain around 400 to 600 grams per month (a far cry from their birth weight) and grow approximately 2cm in length. 

However, it’s essential to remember that every baby is unique, and growth rates can vary. Your GP or Child and Family Health Nurse will track their growth during regular check-ups to ensure they are developing as expected.

Your 4-month-old baby's health

As your child’s development continues to grow, their health remains a top priority. At four months old, your little one is likely thriving, but it’s essential to remain vigilant about their well-being. Here are some key aspects of your baby’s health to keep in mind.

Vaccinations: As a 4-month-old, your baby may have received several rounds of vaccinations to protect them from various diseases. These vaccines are crucial for building immunity and safeguarding your baby’s health. Ensure you follow the recommended vaccination schedule provided by your healthcare provider and keep track of upcoming immunisations.

Regular check-ups: Routine well-baby visits with your doctor or Child and Family Health Nurse are essential for monitoring your baby’s development and growth, as well as addressing any health concerns. During these visits, your doctor will conduct physical examinations, assess developmental milestones and growth from birth weight, and provide guidance on nutrition, sleep, and safety.

Skincare: Your baby’s delicate skin requires gentle care to prevent irritation and discomfort. Keep your baby’s skin clean and moisturised, using mild, fragrance-free products specifically formulated for infants. Protect their skin from sun exposure by dressing them in lightweight clothing and using a broad-spectrum sunscreen on exposed areas if necessary.

Oral health: Even though your baby may not have teeth yet, oral hygiene is still important. Clean your baby’s gums daily with a soft, damp cloth to remove bacteria and prevent the build-up of plaque. Once teeth emerge, transition to a soft-bristled toothbrush and fluoride-free toothpaste designed for infants.

Respiratory health: Babies are susceptible to respiratory infections, especially during the colder months. To minimise the risk of illness, avoid exposing your baby to cigarette smoke and other respiratory irritants. Keep their environment clean and well-ventilated, and wash your hands frequently to reduce the spread of germs and help disease control.

Eye care: Your baby’s eyes are delicate and require gentle care. Keep their eyes clean by wiping them with a clean, damp cloth as needed, starting from the inner corner and wiping outward. If you notice any signs of eye irritation or discharge, consult your doctor promptly for evaluation and treatment.

Gastrointestinal health: Digestive issues such as gas, colic, and reflux are common in babies and can cause discomfort. Feed your baby slowly and burp them frequently during feedings to reduce air swallowing and prevent gas build-up. If your baby experiences persistent digestive problems or shows signs of dehydration, consult your doctor for guidance.

By prioritising your baby’s health and well-being, you can help them thrive during their first year of life and beyond. Stay informed about important health topics, seek guidance from healthcare professionals when needed, and trust your instincts as a parent.

4-month-old baby food milestones

As your baby approaches the four-month mark, you may want to start considering the introduction of solid foods. The current Australian guidance is that you should start introducing solid foods when your baby shows signs of being ready. This is around 6 months but not before 4 months. During the first six months, no matter their birth weight, most breastfed babies or formula-fed babies get all the nutrients and hydration they need for healthy growth and development. 

The World Health Organisation (WHO) recommends exclusive breastfeeding for the first six months of life. When solid foods are introduced, it should be alongside breastfeeding or infant formula. Introducing solids like baby cereal should only be done on the advice of your doctor or your Child and Family Health Nurse. 

Water is not necessary for most babies under six months of age, as breast milk or formula provides adequate hydration. Introducing water too early can fill up your baby’s tiny stomach, potentially reducing their intake of essential nutrients from breast milk or formula.

Watch for signs of readiness in the next few months such as sitting up with support, showing interest in what you’re eating, and losing the tongue-thrust reflex.

If you have any questions or concerns about feeding your baby, consult with your doctor or Child and Family Health Nurse. They can provide guidance on your baby’s individual needs and help you navigate the transition to solid foods when the time is right.

Development tips for your 4-month-old

Encourage tummy time: Help strengthen your baby’s neck and upper body muscles by incorporating tummy time into their daily routine. Start with short sessions and gradually increase the duration to 1-2 hours in total throughout the day as your baby grows more accustomed to this position.

Engage in interactive play: Stimulate your baby’s development, senses and cognitive development through interactive play. Use toys with different textures, shapes, and colours to engage their curiosity and encourage exploration.

Promote language development: Talk, sing, and read to your baby regularly to support their language development. Describe the world around them, narrate your daily activities, and introduce them to new words and sounds.

Provide safe exploration opportunities: Create a safe environment for your baby to explore and discover. Offer age-appropriate toys and objects that encourage reaching, grasping, and exploring with their hands and mouth.

Establish a bedtime routine: Help your baby develop healthy sleep habits by establishing a consistent bedtime routine. Dim the lights, engage in calming activities, such as bathing or reading, and create a soothing sleep environment to promote relaxation and restful sleep.

Monitor developmental milestones: Keep track of your baby’s developmental milestones and celebrate their achievements. Most babies develops at their own pace, so be patient and supportive as they reach new milestones in their journey.

Seek support and guidance: Don’t hesitate to reach out to healthcare professionals, parenting groups, or trusted family members for support and guidance. Parenting can be challenging at times, but you’re not alone, and there are resources available to help you navigate this journey.

Items you will need this month

Nappies: Stock up on nappies in the appropriate size for your baby’s weight. Consider purchasing a combination of disposable and cloth nappies based on your preferences and lifestyle.

Baby clothes: Ensure you have a sufficient supply of baby clothes, including onesies, sleepers, bodysuits, socks, and hats. Choose soft, breathable fabrics that are gentle on your baby’s delicate skin, many babies prefer the feel of these. 

Feeding supplies: If you’re breastfeeding, you may need nursing bras, breast pads, and nipple cream. For formula feeding, have bottles, teats, formula, and a bottle brush on hand. Consider investing in a breast pump if you plan to express milk.

Swaddle blankets: Swaddling can help soothe and comfort many babies, so have a few swaddle blankets ready. Choose lightweight, breathable fabrics that allow for proper airflow.

Baby monitor: Consider investing in a baby monitor to keep an eye on your 4-month-old while they sleep or play in another room. Choose a monitor with features such as video monitoring, temperature sensors, and two-way audio.

Healthcare supplies: Keep a supply of baby-friendly toiletries, including gentle soap, shampoo, lotion, and a baby brush or comb. Have a digital thermometer on hand for monitoring your baby’s temperature.

Baby toys: Choose age-appropriate toys that stimulate your baby’s senses and encourage exploration and play. Look for toys with contrasting colours, different textures, and interactive features.

Nursing pillow: A nursing pillow can provide support and comfort during breastfeeding sessions. Look for a pillow with adjustable straps and a washable cover for convenience.

Burp cloths and bibs: Stock up on burp cloths and bibs to catch spit-up and dribbles during feeding times. Choose soft, absorbent fabrics that are easy to clean.

Baby carrier or sling: Consider investing in a baby carrier or sling for hands-free carrying and bonding with your baby. Choose a carrier that provides proper support for your baby’s developing spine and hips.

Checklist for this month

Schedule well-baby checkup: Book your baby’s 4-month-old well-baby check-up with your GP or Child and Family Health Nurse. Regular check-ups are essential for monitoring your baby’s growth and development, as well as addressing any concerns or questions you may have.

Monitor growth and development: Keep track of your baby’s milestones and growth patterns. Take note of any changes or concerns to discuss with your GP or Child and Family Health Nurse during the check-up.

Engage in interactive play: Spend quality time playing and bonding with your 4-month-old. Use toys, music, and simple games to stimulate their senses and promote cognitive development.

Practise safe sleep: Ensure your baby’s sleep environment is safe and conducive to restful sleep. Follow safe sleep guidelines, including placing your baby on their back to sleep and removing soft bedding and toys from the cot. Once baby has started to roll their arms, they’ll need to be out of the swaddle or sleep sack. 

Maintain feeding routine: Stick to a consistent feeding schedule, whether breastfeeding, formula feeding, or a combination of both. Monitor your baby’s feeding habits and adjust as needed to meet their changing needs.

Stay connected: Seek advice and support from other parents, healthcare providers, and support groups. Don’t hesitate to reach out if you have questions or concerns about your baby’s health and development.

Practise self-Care: Remember to take care of yourself as well. Parenting can be demanding, so prioritise self-care activities such as getting enough rest, eating healthily, and seeking support when needed.

Continue bonding activities: Use everyday activities such as feeding, bathing, and cuddling to strengthen your bond with your baby. Respond promptly to their needs and provide plenty of love and affection.


Baby Development Milestones, Tresillian. Available at: https://www.tresillian.org.au/baby/development/?gad_source=1&gclid=Cj0KCQjwpNuyBhCuARIsANJqL9PPUm5vF1IeZo8wREwEYFCZknnqlm-t9fCgTky5Ho0TYpLTDktex0oaAr3xEALw_wcB 

Introducing solids: Why, when, what and how (2023) Raising Children Network. Available at: https://raisingchildren.net.au/babies/breastfeeding-bottle-feeding-solids/solids-drinks/introducing-solids

Your baby’s growth and development – 4 months old, Pregnancy, Birth and Baby. Available at: https://www.pregnancybirthbaby.org.au/babys-growth-and-development-4-months-old#:~:text=4%20month%20old%20babies%20can,rather%20than%20cry%20at%20times

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