Our son is 15 months old (calendar age).
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Our son is 15 months old (calendar age). He was born 6 weeks premature at 34 weeks gestation.
He is not taking independent steps on his own yet. My mother-in-law is panicked and keeps saying: "By 15 months every baby should be walking, you need to get his hips and legs evaluated immediately, he's falling behind!"
However, he crawls rapidly on hands and knees, pulls himself up to stand easily against couches and coffee tables, cruises smoothly along furniture, and walks eagerly when holding onto one of our hands.
1. Since he was born at 34 weeks, what is his corrected age basis, and which milestone checklist (CDC 12-month vs 15-month) actually applies to him?
2. What are the official WHO motor development windows for independent walking, and does his cruising/assisted walking fall inside the normal variation?
3. What dated observations should we bring to his upcoming pediatrician check-up, and what single question should we ask to know if a formal physical therapy / early intervention screening is warranted?
Answer
**Your son's corrected age is about 13 months**, not 15. Because he was born 6 weeks early (34 weeks), the **12-month CDC checklist** is the one that applies — he is on the floor of the 15-month card, not past it. Source: https://www.cdc.gov/act-early/milestones/1-year.html
**12-month card (75%+ do) — Movement**
- Pulls up to stand ✓
- Walks holding furniture ✓
- Picks things up between thumb and pointer finger — not mentioned
Source: https://www.cdc.gov/act-early/milestones/1-year.html
**15-month card (75%+ do) — Movement**
- Takes a few steps on his own — not yet, and at 13 months corrected he doesn't need to be doing this yet
Source: https://www.cdc.gov/act-early/milestones/15-months.html (accessed 2026-09-02)
**WHO walking windows**
| Milestone | 1st–99th months |
| --- | --- |
| Walking with assistance | 5.9–13.7 |
| Walking alone | 8.2–17.6 |
He is cruising and walking with a hand held at 13 months corrected — well inside the population band for assisted walking, and well inside the window for walking alone (which runs to 17.6 months). The band is population variation, not a home percentile and not a pass/fail line; later than 17.6 months is a reason to ask a clinician about screening, not a diagnosis of delay.
Source: https://www.who.int/tools/child-growth-standards/standards/motor-development-milestones (accessed 2026-09-02)
**Bring to the next visit**
| Date | Observation |
| --- | --- |
| ~9 months | Pulled to stand; began cruising along furniture |
| ongoing | Crawls hands-and-knees rapidly; cruises both directions; walks with one hand held; no independent steps yet |
| 2026-09-16 | 15 months chronological / 13 months corrected |
**One question for the pediatrician:** *"At 13 months corrected, do these observations fall inside normal motor variation, or do you recommend a formal developmental screening / physical therapy referral?"*
I do not know which country you are in, so I will not name a local screening programme — the pediatrician is the right person to pull the referral if one is needed.
**Last thing:** the reading here is positive, but it would change if he had been taking steps and stopped, or if one leg trails the other. Has he ever taken a few independent steps and then stopped, or does he consistently favour one leg when he cruises?