Nationwide, the proportion of certified nurse-midwife (CNM)-attended births has increased steadily. We examined trends in CNM-attended singleton spontaneous vaginal births between 1995 and 2004 in Washington State by site of birth, payer source, and hospital birth volume. CNMs were more likely than other providers to care for women at risk for adverse outcomes based on several sociodemographic indicators. The increased rate of CNM-attended births occurred primarily in hospitals and among both Medicaid- and privately-funded births. The rate of CNM-attended births doubled in hospitals with high birth volumes. We recommend future research designed to understand these trends.