This dataset contains percent preterm and very preterm live births by race/ethnic group of mother. Preterm births are all live births less than 37 weeks of gestation. Very preterm births are all live births less than 32 weeks of gestation. Important growth and development occur throughout pregnancy, especially in the final months and weeks. There is a higher risk of serious disability or death the earlier a baby is born. Gestational age is based on obstetric estimate at delivery (OE). Data includes births with gestational age of 17-47 weeks. Note: The race and ethnic groups in this table utilize eight mutually exclusive race and ethnicity categories. These categories are Hispanic and the following Non-Hispanic categories of Multi-Race, African-American, American Indian (includes Eskimo and Aleut), Asian, Pacific Islander (includes Hawaiian), White (includes Other race) and Unknown (includes refused to state and missing). Data should not be compared to other data where gestational age is based on the date of last normal menses (LMP) and not OE. The National Center for Health Statistics recently transitioned to using an OE-based gestational age measure due to increasing evidence of its greater validity compared with the LMP-based measure. (http://www.cdc.gov/nchs/data/nvsr/nvsr64/nvsr64_05.pdf)