What is the difference (health disparity) in prenatal care for 16 to 45-year-old women with Medicaid versus the general population?

According to Oberg, Lia-Hoagberg, Hodkinson, Skovholt, and Vanman (see the citation below), women who don't have any insurance or who have Medicaid (the health insurance program for the poor) have fewer visits to the doctor when pregnant and start receiving care later in the pregnancy than women with private health insurance.

The book Prenatal Care: Reaching Mothers, Reaching Infants, edited by S.S. Brown (see the citation below), cites research by Cooney, who found that women in New York City in several different sub-categories defined by race, age, and marital status received later prenatal care and fewer doctor visits when they had Medicaid compared to women with private health insurance. Other studies in other areas of the United States confirmed these findings. Researchers believe that this might be because enrolling in Medicaid takes time and delays pregnant women's first visit to receive prenatal care. In addition, research suggests that clinics that serve women on Medicaid may be crowded, and therefore women have to delay their care. In addition, research suggests that women on Medicaid are more likely to have low socio-economic status, less education, be in poor health, and be under 20, which are all factors that are associated with less prenatal care. In addition, research in some states (see "The Birth Certificate and Medicaid Data Match Project: Initial Findings in Infant Mortality 4 Minnesota Department of Health – 2005") has found that infant mortality is higher for mothers who are in some groups of Medicaid.  

Citations:

Oberg, Lia-Hoagberg, Hodkinson E, Skovholt C, Vanman R. Prenatal care comparisons among privately insured, uninsured, and Medicaid-enrolled women. Public Health Rep. 1990 Sep-Oct;105(5):533-5. 

Prenatal Care: Reaching Mothers, Reaching Infants. Institute of Medicine (US) Committee to Study Outreach for Prenatal Care; Brown SS, editor. Washington (DC): National Academies Press (US); 1988.

The Birth Certificate and Medicaid Data Match Project: Initial Findings in Infant Mortality 4 Minnesota Department of Health – 2005.