Medicaid Outreach and Child Health Act of 1990 - Amends title XIX (Medicaid) of the Social Security Act to set the Federal share of the costs of carrying out a Medicaid outreach program for pregnant women and children at 75 percent of such costs.

Directs the Secretary of Health and Human Services to establish a demonstration program to assist community organizations in developing innovative approaches to increase the participation of pregnant women and children in the Medicaid program. Authorizes appropriations for such demonstration program through FY 1993.

Requires States to continue the Medicaid eligibility of pregnant women through the month which includes the 60th day following their pregnancies and to children under age one regardless of changed circumstances which would otherwise render them ineligible for such benefits.

Permits States to continue a child's Medicaid eligibility for one year after such eligibility would otherwise cease.