Almost two-thirds of pregnant women who are on Medicaid or who lack health insurance receive inadequate medical care during their pregnancies, a major contributing factor to high infant mortality rates, according to a survey of such women in 32 U.S. communities by the General Accounting Office.

The new GAO report will be released today at a hearing of the House Government Operations human resources subcommittee. A copy of the draft report was provided to The Washington Post.

The study found that women who had either Medicaid or no health insurance were far less likely than women with private insurance to seek care during the first three months of pregnancy, as is recommended, or to see a doctor at least nine times during pregnancy.

Lack of prenatal care is known to raise the chances of a woman's having a low-birth-weight baby, one that weighs less than 5 1/2 pounds. Such infants are 40 times more likely than normal-weight babies to die during the first four weeks of life.

The United States has one of the highest infant mortality rates of any industrialized country, with about 1 percent of infants -- approximately 40,000 a year -- dying during their first year of life.

For its study, the GAO interviewed 1,157 women in 32 communities in eight states, who had either Medicaid or no health insurance. Nationally, about 17 percent of women of reproductive age have no health insurance and 9 percent are covered only by Medicaid, according to the report.

About 63 percent of the women surveyed had inadequate prenatal care. More than 12 percent of the women surveyed had low-birth-weight babies, compared with a national rate of less than 7 percent. Lack of money, lack of transportation and unawareness of the pregnancy were among the reasons most often cited by women for not seeking medical care. Women with no insurance were less likely to receive care than those on Medicaid, the survey found.