Definition: Percentage of infants born prior to 37 weeks of gestation, based on obstetric estimate of gestational age (e.g., in 2022, 9.1% of infants born to California mothers were born preterm).
Data Source: California Dept. of Public Health, Birth Statistical Master Files (Mar. 2020); CDC WONDER, Natality Data (Mar. 2024).
Footnote: County-level data reflect the mother's county of residence, not the county in which the birth occurred. Data exclude infants for whom obstetric estimates of gestation were not reported. For years 2017 and earlier, the notation S refers to numbers and rates that have been suppressed because there were fewer than 20 cases of infants born preterm. For years 2018 and later, the notation S refers to numbers that have been suppressed because there were fewer than 10 cases, rates that have been suppressed because there were fewer than 20 cases, and numbers and rates that have be suppressed because the total county population was lower than 100,000. N/A means that data are not available.
