Adjusted odds ratio of PTB in New Mexico, 1991-2005. Maternal reference age = 25-29. Maternal reference education level = 9-12 years. Maternal reference ethnicity = White Non-Hispanic. The age group with the lowest odds for PTB in the state of New Mexico is 25-29 years. The odds for PTB were higher among younger and older parturients compared to women 25-29 years of age. Maternal education beyond 12 years was associated with significantly decreased odds of PTB in New Mexico. The ethnic group with the highest odds for PTB was Blacks and the lowest was Native Americans.