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Background: Preterm birth (PTB) is a significant health problem both in New Mexico and nationally. It accounts for significant infant morbidity and mortality and it poses an economic burden to both individuals and the state. The goal of this study is to elucidate maternal risk factors for PTB in New Mexico, a poor state with a unique ethnic background. By doing this we hope to be able to identify women at increased risk and invite further study into targeted interventions among these high risk populations. Methods: This was a cross-sectional analysis of 377,770 singleton live births in the state of New Mexico from 1991-2005. The medical risk factors tracked were pulmonary, renal, cardiac, diabetes, eclampsia, oligo/polyhydramnios, hypertensive disorders, cervical incompetence, previous preterm delivery, tocolysis and isoimmunization. Gestational age of less than 37 weeks was defined as PTB. Multiple gestations and congenital anomalies were excluded. The Kotelchuck Index was used as a measure for level of prenatal care described as inadequate, intermediate, adequate, and intensive. Multivariate logistic regression was conducted using SAS 9.1 statistical software. Results: Of the live births analyzed, 28,036 of these were preterm (7.4%). Overall the PTB rate has risen from 1991-2005 at a rate of 0.18 percent per year. This was statistically significant (p = <0.00004). Among patients with medical risk factors, PTB rate had a direct inverse relationship with an intensive level of prenatal care. High risk patients with intensive care were less likely to have a PTB delivery with an odds ratio of 0.74 than similar patients with low levels of care. The nadir for risk of PTB is among women aged 25-29 with significant increases in risk among women <15 and >40 years of age. Other risk factors are unmarried status, education less than high school,tobacco/alcohol use, Black, Asian, and White Hispanic ethnicity and the presence of one or more medical risk factors. Statistically significant protective factors for PTB are age 25-29, education surpassing high school, and Native American race. Counties with rising adjusted PTB rates are Chaves, Dona Ana, Grant, Hidalgo, Lea, Lincoln, McKinley, Mora, Otero, Rio Arriba, San Juan and San Miguel. Counties with decreasing PTB rates are Sandoval and Santa Fe counties. Conclusion: Even adjusted for known risk factors PTB is still a significant problem in New Mexico. A lack of prenatal care was a significant predictor of PTB in high risk patients. Other predictors include the known risk factors of age <15 and >40, single, tobacco/alcohol use, being of low socioeconomic status and White Hispanic, Asian and Black ethnicities. Interestingly, Native American patients have a lower PTB rate compared to other groups, even though this group is traditionally one of low socioeconomic status in New Mexico.