U.S. Mean Age of Mother at First Birth

## What this measures

The average age, in years, of mothers giving birth to their first child in the United States in a year. Annual, final data, from 2003: WONDER's "Average Age of Mother" for births of live-birth order 1.

## Why it matters

It is the single number that best summarizes the delay in starting a family. A later first birth leaves fewer years for later children, so it bears on completed family size as well as on maternity care and careers.

## How to read it

Years of age. It moves slowly, by a tenth or two of a year in most years, so a change of half a year is large. Compare it with the shares of births by age (demography.cdc.births_share.mother_age.*).

## What it does not say

It covers first births only, and only those whose birth order is recorded. The 1995-2002 database has no birth order, so the series starts in 2003. It is an average, so it does not show how spread out first births are. Final data only; the newest year appears about nine months after it ends.

## Source

CDC WONDER Natality databases (wonder.cdc.gov): 1995-2002, 2003-2006 and 2007 to the latest final year, from the National Vital Statistics System birth certificates compiled by the National Center for Health Statistics (NCHS). Read through the WONDER API, national figures only. Public domain; use does not imply CDC endorsement. WONDER's data-use restrictions apply: health statistical reporting and analysis only, and no count of 9 or fewer is published. Palanor checks monthly; NCHS adds a final year once a year.