Baby age

Just the date of birth: completed weeks and months. If born before 37 weeks, also the corrected age used for growth and milestones.

Date of birth

Born preterm (before 37 weeks)

Weeks or months?

In the first months everything is counted in weeks (checkups, vaccines, development): “12 weeks” is more precise than “almost 3 months”. The tool gives both, consistent with how paediatricians count: completed calendar months, not 30-day blocks.

Corrected age for preemies

A baby born at 32 weeks is 8 weeks “early” on term (40): at 3 calendar months, development compares to a 1-month-old. That's corrected age: normally used up to 24 months for growth, percentiles and milestones (smiling, grasping, crawling). Our growth percentile tool uses exactly the age in months.

Note

Worldwide about 1 in 10 babies is born preterm: corrected age is the standard neonatology convention. Informational tool: assessments and follow-up belong to your paediatrician and, for very preterm babies, the neonatal follow-up clinic.