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Developmental milestones by age

Sophie Acott

Sophie Acott

Certified sleep consultant · Author of Sleep Play Love · 13 years

Published January 17, 2023 · Updated July 17, 2026

The short answer

Milestones and sleep are deeply linked. From 0 to 24 months, growth spurts, teething, rolling, crawling, walking, separation anxiety, and mental leaps all commonly trigger sleep regression lasting two to six weeks. Expect catnaps, night waking, and bedtime resistance. Meet these phases with an optimized sleep environment, an age-appropriate routine, connection through play, and extra cuddles. This too shall pass.

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Every time I mention developmental milestones to weary, sleep deprived parents, I see them cringe; usually, because these 'milestones' generally equate to irritability, sleep regression, and heightened clinginess (aka a parental nightmare).

But these times are also an essential period of great growth, development, maturity, and learning cool new skill sets which form the foundations for all physical capabilities, social interactions, and intellect for later life.

The first 12-24 months and beyond is a time of constant evolution, and although your baby is learning all the time, from my experience, the common ages (and milestones) affecting sleep and behavior are as follows:

0-3 months: 4-6 months: 7-9 months: 10-12 months:

This is the general answer.
Your little one deserves a specific one.

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13-14  months: 18 Months Click here for a comprehensive (printable) guide  to developmental milestones from 0-6 years. Trust in your child's ability and natural progression; all babies are individuals, and will have their own unique inborn timeline. They will be capable of achieving each milestone as they are ready to, with limited parental intervention. Of course, if you are concerned about your child's progression, consult your healthcare professional.

EFFECTS ON SLEEP:

Sleep regression is extremely common at these times - lasting anywhere between two to six weeks or more. Some changes you may notice with sleeping patterns include:  

SOLUTIONS:

S

Sophie

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Before I could really answer this for you, I'd ask two things.

Tap one and I'll start your plan there. No judgment — there never is.

Above all, try to remain patient, kind and sensitive to your baby's needs. Extra cuddles will make them feel loved and secure....And know that this too shall pass!

TIP: Be sure to rule out any medical reasons for frequent wakings, fussiness, or change in sleep patterns first and foremost before following the recommendations mentioned above, or embarking on a new sleep routine/program. Every child reaches milestones at an individual pace. For any concerns regarding your child's development, contact your healthcare professional. 

"You are a good parent, you are doing your best, and you are enough."

— Sophie, from the book

Tonight can be night one.

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