The "Cadillac" of pain control during labor is the epidural, an anesthetic injected into the epidural space surrounding the spinal cord. It eliminates pain, allows the mother to remain awake and has no effect on the newborn.

Whether a laboring woman receives an epidural or other pain control, however, depends on her insurance type, a UB study has found.

Results of the study, appearing in the May issue of Journal of Health Care for the Poor and Underserved, show that women who are residents of New York State and covered by Medicaid are less than half as likely to receive an epidural for vaginal delivery than mothers with HMO or private coverage.

Further, Medicaid recipients undergoing cesarean section were twice as likely as mothers with HMO or private coverage to receive general anesthesia, which renders the mother unconscious and increases the risk of adverse effects on the mother and her baby.

"The study provides evidence of differences across New York State in the availability of obstetrical pain control which, until now, have not been well measured," said Thomas E. Obst, director of the Nurse Anesthesia Program in the School of Nursing, and lead author on the study. "Furthermore, the study points to the need for a national assessment of the availability of pain control options for obstetrical patients."

The study's findings are based on a review of records for 121,351 women who gave birth in 1992 in upstate New York, which excludes New York City. The researchers also excluded multiple births, forceps births and records from hospitals reporting fewer than six live births in 1992.

Of the total women in the study, all but 1 percent had insurance: 51 percent had private coverage, 28 percent Medicaid, 20 percent managed care and the remaining were characterized as self-pay. Seventy-five percent had vaginal deliveries (excluding forceps) and 81 percent received some type of anesthesia.

Results showed considerable variation among women with vaginal deliveries in the use of either no anesthesia or epidural anesthesia, based on the type of insurance. During vaginal delivery, 18 percent of women with HMO coverage and 21 percent with private insurance received an epidural, compared to about 9 percent of Medicaid mothers.

Among those receiving no anesthesia for vaginal delivery, however, Medicaid mothers dominated, with 36 percent compared to 18 percent of women with HMO coverage and 22 percent with private insurance. For cesarean delivery, nearly 50 percent of women with private or HMO coverage received an epidural, compared to only 25 percent of those covered by Medicaid, the majority of whom received the riskier general anesthesia.

While the type of insurance had the most significant bearing on the type of anesthesia women received, ethnicity also appeared significant, Obst said. Results showed that Caucasian mothers were more likely to receive an epidural for vaginal delivery and either a spinal or epidural for cesarean delivery than African-American mothers.

Obst noted that the disparities revealed by this study raise questions about the reimbursement for and availability of obstetrical-anesthesia care that need answers. "We also need to understand how much patient preference and cultural mores influence the use of a particular anesthesia intervention," he said.

The study suggests that these clinical decisions are based on complex factors that include the mother, obstetrical-care provider, anesthesia-care provider and the health-care system at large, he said. "One should not be under the delusion that pain management, like many other aspects of the American health-care system, is available based primarily on ethically determined premises," Obst stated.

Also participating in the study were Eric Nauenberg, formerly at UB, now at the Toronto Ministry of Health and Long-term Care and the University of Toronto, and Germaine M. Buck, formerly at UB, now at the National Institutes of Health.

The study was supported by the New York State Department of Health and the American Hospital Association.