My Baby Seems to Use One Side More Than the Other
Medically reviewed by Dr. Sarah Chen, MD, FAAP · Board-Certified Pediatrician
Content reviewed against published AAP, CDC, AAP guidelines
Last reviewed:
Your baby's physical development is unique, and concerns about seems to use one side more than the other, here is what you need to know.
The short answer
Babies should use both sides of their body fairly equally during the first 18 months of life. While slight preferences can be normal, a consistent pattern of favoring one side - using one arm much more than the other, crawling with one leg dragging, or turning the head predominantly one way - should always be discussed with your pediatrician. Early identification of asymmetry leads to the best outcomes.
Key takeaways
- Babies should use both sides of their body fairly equally during the first 18 months of life. While slight preferences can be normal, a consistent pattern of favoring one side - using one arm much more than the other, crawling with one leg dragging, or turning the head predominantly one way - should always be discussed with your pediatrician. Early identification of asymmetry leads to the best outcomes.
- Usually normal when: Your baby occasionally prefers one hand for a specific activity but uses both hands well overall.
- Call your doctor if: Your baby suddenly stops using one arm or leg after previously using both equally - acute onset of one-sided weakness is a medical emergency.
- Varies by age — see the age-by-age breakdown below
“Supervised tummy time is recommended daily from the time the baby comes home from the hospital to help prevent flat head syndrome and to strengthen neck and shoulder muscles.”
Parents everywhere have the same worry. You are doing the right thing by looking into it.
What Parents Should Know
According to AAP, CDC guidelines, babies should use both sides of their body fairly equally during the first 18 months of life. While slight preferences can be normal, a consistent pattern of favoring one side - using one arm much more than the other, crawling with one leg dragging, or turning the head predominantly one way - should always be discussed with your pediatrician. Early identification of asymmetry leads to the best outcomes. At 0-3 months, newborns may briefly prefer turning their head to one side, but their arm and leg movements should be fairly symmetric. If your baby consistently keeps one hand fisted while the other is open, or if one arm moves much less than the other, bring this to your pediatrician's attention. Torticollis (tight neck muscles causing a head-turn preference) is common and very treatable at this age. It is generally considered normal when your baby occasionally prefers one hand for a specific activity but uses both hands well overall. However, you should contact your pediatrician promptly if your baby suddenly stops using one arm or leg after previously using both equally - acute onset of one-sided weakness is a medical emergency.
Normal vs. Concerning
By Age
What to expect by age
0-3 months
Newborns may briefly prefer turning their head to one side, but their arm and leg movements should be fairly symmetric. If your baby consistently keeps one hand fisted while the other is open, or if one arm moves much less than the other, bring this to your pediatrician's attention. Torticollis (tight neck muscles causing a head-turn preference) is common and very treatable at this age.
4-6 months
By this age, babies should be using both hands to reach for and grasp toys and should kick both legs equally. If you notice your baby consistently reaching with only one hand, or if one leg seems stiffer or less active than the other, mention it to your doctor. These observations are valuable - parents are often the first to notice subtle asymmetries.
7-9 months
When crawling develops, watch for symmetry. Some babies have an "imperfect" crawl that still uses both sides, which is fine. But if your baby consistently drags one leg, uses one arm differently, or leans heavily to one side, an evaluation is important. Asymmetric crawling can sometimes indicate a difference in tone or strength between the two sides.
10-18 months
As your baby starts pulling up, cruising, and walking, symmetry becomes easier to observe. Both legs should bear weight equally, and your baby should use both hands during play. If one side is clearly weaker or less coordinated, a referral to a pediatric neurologist or physical therapist is recommended. Early intervention can make a significant difference.
What to Tell Your Pediatrician
- Describe when you first noticed seems to use one side more than the other and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby consistently uses one hand much more than the other before 18 months.
- Mention if your baby turns their head strongly to one side and resists turning to the other.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your baby occasionally prefers one hand for a specific activity but uses both hands well overall.
- Your baby has a slight head-turn preference in the first few weeks that is resolving with repositioning.
- Your baby crawls with a slightly asymmetric pattern but uses both arms and legs actively.
- Your toddler over 18 months is developing a natural hand preference - this is appropriate at that age.
- Your baby consistently uses one hand much more than the other before 18 months.
- Your baby turns their head strongly to one side and resists turning to the other.
- Your baby crawls with one leg dragging or tucked underneath while the other pushes.
- When your baby stands or walks, one leg seems stiffer, weaker, or positioned differently than the other.
- Your baby suddenly stops using one arm or leg after previously using both equally - acute onset of one-sided weakness is a medical emergency.
- One side of your baby's body seems consistently stiff or rigid while the other side moves normally.
- Your baby has asymmetric movement combined with seizure-like episodes, unusual eye movements, or changes in alertness.
What You Can Do at Home
- Keep track of when you notice seems to use one side more than the other — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby occasionally prefers one hand for a specific activity but uses both hands well overall — this is generally within the range of normal.
- At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Provide plenty of supervised floor time and tummy time to support your baby's physical development.
- While monitoring at home, seek immediate care if your baby suddenly stops using one arm or leg after previously using both equally - acute onset of one-sided weakness is a medical emergency.
Related Resources
Milestone Checklists by Age
Track your baby's developmental milestones from birth to 5 years with age-specific checklists.
Month-by-Month Development
Detailed monthly development guides from birth through 24 months.
When to Call the Doctor
General guide on when to call the pediatrician, visit urgent care, or go to the ER.
Frequently asked questions
Is seems to use one side more than the other normal?
When should I call the doctor about seems to use one side more than the other?
When is seems to use one side more than the other normal?
What causes seems to use one side more than the other?
What should I mention to my pediatrician about seems to use one side more than the other?
Is seems to use one side more than the other normal at 0-3 months?
Is seems to use one side more than the other normal at 4-6 months?
Should I go to the ER for seems to use one side more than the other?
Does seems to use one side more than the other go away on its own?
References
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss My Baby Seems to Use One Side More Than the Other.
Things to mention
- Describe when you first noticed seems to use one side more than the other and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if your baby consistently uses one hand much more than the other before 18 months.
- Mention if your baby turns their head strongly to one side and resists turning to the other.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- Your baby consistently uses one hand much more than the other before 18 months.
- Your baby turns their head strongly to one side and resists turning to the other.
- Your baby crawls with one leg dragging or tucked underneath while the other pushes.
Urgent signs to report immediately
- Your baby suddenly stops using one arm or leg after previously using both equally - acute onset of one-sided weakness is a medical emergency.
- One side of your baby's body seems consistently stiff or rigid while the other side moves normally.
- Your baby has asymmetric movement combined with seizure-like episodes, unusual eye movements, or changes in alertness.
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members
Related Resources
Bottom line
Most cases of seems to use one side more than the other are normal. Talk to your pediatrician if your baby suddenly stops using one arm or leg after previously using both equally - acute onset of one-sided weakness is a medical emergency.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
Was this page helpful?
Related Physical Concerns
Should I Use Adjusted Age for My Preemie's Milestones?
Yes — for premature babies, developmental milestones should be assessed using adjusted (corrected) age, not chronological age, until at least 2 years of age. Adjusted age is calculated by subtracting the number of weeks your baby was born early from their actual age. For example, a 6-month-old born 2 months early would have an adjusted age of 4 months, and should be assessed against 4-month milestones. Most pediatricians use adjusted age for developmental assessment through age 2-3, and for growth charts through age 2.
Baby-Proofing a Small Apartment
Baby-proofing a small apartment is absolutely possible and focuses on the same key safety principles as any home: securing furniture to walls, covering outlets, locking cabinets with hazardous materials, and ensuring safe sleep spaces. Small spaces actually have an advantage - there is less area to monitor. Focus on eliminating the most dangerous hazards first: falls, poisoning, choking, and burns.
My Baby Only Army Crawls
Army crawling (also called commando crawling) is a completely valid and normal way for babies to move. Many babies army crawl for weeks or even months before transitioning to hands-and-knees crawling, and some skip hands-and-knees crawling entirely. What matters is that your baby is independently mobile and exploring their environment.
One Side of My Baby's Body Moves Differently
Babies should generally use both sides of their body equally. If one side consistently moves differently, is weaker, stiffer, or less coordinated, this warrants evaluation. Asymmetric movement can indicate hemiplegia (cerebral palsy affecting one side), brachial plexus injury, or other neurological conditions that benefit from early therapy.
My Baby Crawls Unevenly
While some variation in crawling patterns is normal, consistently favoring one side or dragging one limb while crawling warrants attention. Babies should use both arms and both legs relatively equally when crawling. Persistent asymmetry could indicate muscle tone differences, hip issues, or neurological concerns that benefit from early evaluation.
My Baby Still Has the Fencing Reflex (Persistent ATNR)
The asymmetric tonic neck reflex (ATNR, also called the fencing reflex) causes your baby to extend the arm on the side they are looking toward. It should integrate between 4-6 months. If the ATNR persists strongly beyond 6 months, it can interfere with bringing hands to midline, bilateral hand use, and rolling. Evaluation is recommended.