ANN ARBOR—Midwifery, once an exotic and unregulated profession, is now solidly in the mainstream of health care. Nearly 40 percent of women in a University of Michigan study, who had a choice of either a certified nurse-midwife or an obstetrician, opted for a midwife.

What distinguished the woman who chose a nurse-midwife rather than an obstetrician? An unusually strong belief that she had control over her own health and a corresponding responsibility to use it, according researchers at the U-M School of Nursing and U-M Women’s Hospital. The women who chose nurse-midwives also were more likely to have endured a highly stressful event in their past, and generally planned on breast feeding at least four months.

The study, which included 1,464 women who received maternity care and gave birth at the U-M Women’s Hospital, will be reported in the December issue of the Journal of Women’s Health. The lead authors on the study were certified nurse-midwives Terri L. Murtland and Patricia A. Crane, and nursing Prof. Deborah J. Oakley.

“Patients self-selected either a midwife or an obstetrician when they called for their first appointment,” explained Murtland.” The women in both groups were similar in most ‘external’ respects. They were equally healthy, were of just low to moderate risk in their pregnancies, and averaged 29 years of age. The average education level in both groups was 15 years of schooling and the average income was $20,000 or more.”

On average, the women in both groups were emotionally healthy, the researchers said. Very few were overly fearful about giving birth or being a parent and most were in happy relationships.

“But 23.4 percent of the nurse-midwife group had encountered a highly stressful life event that had affected them or a member of their immediate family, or had threatened their jobs, schooling or finances, compared to 13.9 percent of the obstetrician group,” Crane said. ” It may be that those women were attracted to nurse-midwives by their reputation for holistic and supportive care.”

Women who chose midwives also seemed to have considered the kind of care they wanted more thoughtfully. About 67 percent of the group indicated they specifically wanted the kind of care a nurse-midwife offers while only 25 percent of the obstetrician group said they liked the kind of care an obstetrician offers.

Also, 64 percent of the midwife group said they wanted care from a woman compared with 14 percent of the obstetrician group. Women who chose midwives were also almost twice as likely (47 percent to 25 percent) to have discussed the decision with and been influenced by a friend.

Forty-five percent of the women in the obstetrician group, on the other hand, said they chose an obstetrician because of the Medical Center affiliation, and 25.7 percent had never considered other options. Between 3 percent and 4 percent of them also cited either referral from another health care provider, insurance coverage, self-assessed high risk or a prior low birth weight baby.

“Overall, the results indicate that women who chose nurse-midwives thought about their decisions more,” said Oakley. ” One explanation could be that it takes more consideration and ‘justification’ to make a decision that differs from the usual type of maternity care.”

An alternative explanation could be that women in the nurse-midwife group are the type of women who nearly always consider more options before they make decisions of any kind. ” This explanation is supported by another finding in the study that women in the nurse-midwife group had used a wider variety of birth control methods,” Oakley said.

“Whatever the explanation, it seems clear that a significant proportion of low-risk women can be attracted to nurse-midwifery care,” she added. Although 75 percent of U.S. women have low-risk pregnancies, and would qualify for care by certified nurse-midwives, the National Center for Health Statistics reports that only 4 percent of U.S. births are attended by nurse-midwives.” But as hospitals continue to expand their nurse-midwifery services, those percentages are likely to climb,” Oakley said.