Overall Birth Defect Rates


Birth Defects in California

The overall rate of birth defects is 3%, 1 in 33, of live births and fetal deaths.  This number has remained constant over time and has been reported throughout the United States in a variety of publications.

In California this rate was confirmed by a decade of surveillance data throughout the State on over 200 conditions.  Cases were actively ascertained from medical record review in hospitals, genetics centers, and chromosome laboratories.  Diagnoses to age 1 were included.

To estimate the number of cases of birth defects statewide and in individual counties for a particular year, multiply the number of live births and fetal deaths in that year by 3%.

Birth Defects by Mother’s Age

Mothers under 20 or over 35 have slightly higher risks.   The greater risk in women over 35 is largely due to the higher rate of births with chromosome defects—particularly trisomies, or extra chromosomes.


Percent of Births
    All Birth Defects Birth Defects without Chromosome Defects