Developmental Comparison Anxiety in Twins
Medically reviewed by Dr. Emily Torres, PhD, CCC-SLP · Pediatric Speech-Language Pathologist
Content reviewed against published AAP, CDC, NIH guidelines
Last reviewed:
Behavioral development varies greatly from child to child. If you have noticed developmental comparison anxiety in twins, here is what you need to know.
The short answer
It is completely normal for twins to develop at different rates, even identical twins. Having a built-in comparison can intensify parental worry, but each child has their own developmental timeline. Differences in when twins reach milestones like crawling, walking, or talking are expected and usually do not indicate a problem with either child.
Key takeaways
- It is completely normal for twins to develop at different rates, even identical twins. Having a built-in comparison can intensify parental worry, but each child has their own developmental timeline. Differences in when twins reach milestones like crawling, walking, or talking are expected and usually do not indicate a problem with either child.
- Usually normal when: Your twins reach the same milestone a few weeks or even a couple of months apart - this is within the normal range of variation
- Call your doctor if: Either twin loses previously acquired skills - such as words, walking, or social engagement - at any age
- Varies by age — see the age-by-age breakdown below
This is one of the most common questions parents ask. Searching for answers means you care.
What Parents Should Know
According to AAP, CDC, NIH guidelines, it is completely normal for twins to develop at different rates, even identical twins. Having a built-in comparison can intensify parental worry, but each child has their own developmental timeline. Differences in when twins reach milestones like crawling, walking, or talking are expected and usually do not indicate a problem with either child. At 0-3 months, in the earliest months, developmental differences between twins are often related to birth weight, gestational age, and any NICU time. A twin who was smaller at birth or spent time in the NICU may take a bit longer to reach early milestones like head control or social smiling. These early differences often even out over the first year, especially when adjusted age is taken into account for premature babies. It is generally considered normal when your twins reach the same milestone a few weeks or even a couple of months apart - this is within the normal range of variation. However, you should contact your pediatrician promptly if either twin loses previously acquired skills - such as words, walking, or social engagement - at any age.
Normal vs. Concerning
By Age
What to expect by age
0-3 months
In the earliest months, developmental differences between twins are often related to birth weight, gestational age, and any NICU time. A twin who was smaller at birth or spent time in the NICU may take a bit longer to reach early milestones like head control or social smiling. These early differences often even out over the first year, especially when adjusted age is taken into account for premature babies.
3-6 months
You may notice one twin reaching for toys, rolling, or babbling before the other. This is a normal variation - even singleton siblings born years apart often hit milestones at different ages. Avoid using one twin as the benchmark for the other. Instead, track each child's progress individually against standard developmental ranges.
6-12 months
Differences in motor milestones like sitting, crawling, and pulling to stand can become more noticeable and may feel more anxiety-provoking. Remember that the range of normal for most milestones is wide - crawling, for example, can begin anywhere from 6 to 10 months. Some babies skip crawling entirely. If one twin is consistently lagging across multiple domains, not just one skill, discuss this with your pediatrician.
12-24 months
Language differences often become the most noticeable concern in this period. It is common for one twin to talk earlier or more than the other. Twins as a group tend to start talking slightly later than singletons, partly because they split parental attention and sometimes develop their own communication shortcuts. If one twin has no words by 15-16 months or is not understanding simple instructions, an individual evaluation is appropriate - not because of the comparison to their twin, but based on standard developmental expectations.
24-36 months
By this age, personality and temperament differences are increasingly clear. One twin may be more verbal and social while the other is more physical and independent. These are not deficits - they are individual strengths. However, if one twin is significantly behind in a specific area - for example, using far fewer words, not combining words by age two, or not engaging in pretend play - an individual evaluation is warranted regardless of what the other twin is doing.
What to Tell Your Pediatrician
- Describe when you first noticed developmental comparison anxiety in twins and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if one twin is consistently behind in multiple developmental areas - not just one skill - compared to standard age expectations (not compared to the other twin).
- Mention if one twin has stopped progressing or has lost previously acquired skills such as words or motor abilities.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your twins reach the same milestone a few weeks or even a couple of months apart - this is within the normal range of variation
- One twin is more physically adventurous while the other is more verbal or social - different strengths are common
- Your twins were premature and the smaller or sicker twin is reaching milestones a bit later when using actual age rather than adjusted age
- You feel anxious about the differences even when your pediatrician says both children are developing normally - comparison anxiety is very common in parents of multiples
- One twin is consistently behind in multiple developmental areas - not just one skill - compared to standard age expectations (not compared to the other twin)
- One twin has stopped progressing or has lost previously acquired skills such as words or motor abilities
- The gap between your twins' abilities seems to be widening over time rather than narrowing
- Your anxiety about developmental differences is affecting your ability to enjoy parenting or your bond with one of your children
- Either twin loses previously acquired skills - such as words, walking, or social engagement - at any age
- Either twin shows signs that would be concerning in any child: no babbling by 12 months, no words by 16 months, no two-word phrases by 24 months, or any loss of skills at any age
What You Can Do at Home
- Keep track of when you notice developmental comparison anxiety in twins — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your twins reach the same milestone a few weeks or even a couple of months apart - this is within the normal range of variation — this is generally within the range of normal.
- At 0-3 months, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Respond consistently and calmly to your baby's behavior. Maintain predictable daily routines.
- While monitoring at home, seek immediate care if either twin loses previously acquired skills - such as words, walking, or social engagement - at any age.
Related Resources
Frequently asked questions
Is developmental comparison anxiety in twins normal?
When should I call the doctor about developmental comparison anxiety in twins?
When is developmental comparison anxiety in twins normal?
What causes developmental comparison anxiety in twins?
What should I mention to my pediatrician about developmental comparison anxiety in twins?
Is developmental comparison anxiety in twins normal at 0-3 months?
Is developmental comparison anxiety in twins normal at 3-6 months?
Should I go to the ER for developmental comparison anxiety in twins?
Does developmental comparison anxiety in twins go away on its own?
References
- [1]American Academy of Pediatrics. Developmental Milestones. HealthyChildren.org. AAP
- [2]Centers for Disease Control and Prevention. Important Milestones: Your Child By Age. Learn the Signs. Act Early. CDC
- [3]National Library of Medicine. Language Development in Twins: A Review. Journal of Child Language, 2014. NIH
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Developmental Comparison Anxiety in Twins.
Things to mention
- Describe when you first noticed developmental comparison anxiety in twins and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if one twin is consistently behind in multiple developmental areas - not just one skill - compared to standard age expectations (not compared to the other twin).
- Mention if one twin has stopped progressing or has lost previously acquired skills such as words or motor abilities.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- One twin is consistently behind in multiple developmental areas - not just one skill - compared to standard age expectations (not compared to the other twin)
- One twin has stopped progressing or has lost previously acquired skills such as words or motor abilities
- The gap between your twins' abilities seems to be widening over time rather than narrowing
Urgent signs to report immediately
- Either twin loses previously acquired skills - such as words, walking, or social engagement - at any age
- Either twin shows signs that would be concerning in any child: no babbling by 12 months, no words by 16 months, no two-word phrases by 24 months, or any loss of skills at any age
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 developmental comparison anxiety in twins are normal. Talk to your pediatrician if either twin loses previously acquired skills - such as words, walking, or social engagement - at any age.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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