The health planning agency for Maryland's four southern counties released its five-year proposal yesterday, warning of an excess supply of obstetrical and pediatric beds if those projected are used as planned.

The Southern Maryland Health Systems Agency's draft proposal of its comprehensive health plan for Prince George's St. Mary's, Charles and Calvert counties was released as part of its effort to comply with a 1974 federal law requiring local and state agencies to prepare a plan meeting federal specifications.

Although the proposal finds some shortages in primary care physicians and nurses, fully trained ambulance personnel and some specialized services, the general level of facilities existing and planned for the four countries appears to be adequate to serve the area's population over the next five years.

The plan states, however, that the four counties will need only 60 obstetrical beds by 1983, although 154 are currently planned. The health systems agency recommends that 23 beds at Prince George's General Hospital, which have been certified for use as obstetrical beds, he decertified. Another 36 obstetric beds planned for the soon-to-be-opened Greater Laurel-Beltsville Hospital "should not be opened," the plan asserts.

In a similar vein, the plan states that by 1983 the four counties will have 42 to 45 more pediatric beds than are needed if all those planned are opened. The draft specifically notes that Prince George's General, with about 50 pediatric beds and an annual occupancy rate of 55.3 per cent in 1976, falls below the federal standard of a 65 per cent occupancy rate.

Planning officials and others involved in health care in the Washington metropolitan area have said for several years that the area suffers from an over-supply of hospital beds, which generally raises the cost of hospitalization for virtually everyone in the area.

With the opening last year of the new Children's Hospital in Washington, pressure has increased throughout the area to close surplus pediatric beds in suburban hospitals in order to obtain a more efficient use of resources.

The plan also found that the four counties have an insufficient number of highly trained emergency medical service personnel in ambulances. Response times for emergency vehicles, however, were found to be good and the lack of trained personnel is not considered a severe problem, according to Kevin J. Hayes, a member of the agency's planning staff.

A spokeswoman for the Prince George's Medical Society said the draft has been given to designated members who will study it and offer comments at a public hearing on March 16 at Prince George's Community College in Largo. Another hearing will be held March 14 in Mechanicsville in St. Mary's County.

Federal legislation requires generally that new hospital construction and other health-related facilities be approved by a federally designated local agency that has prepared a plan of health needs. Facilities built without such approval could be denied any federal reimbursement under Medicare - the program offering medical to the elderly - and other programs.

The Southern Maryland plan is the second to be made public in the metropolitan area. The Northern Virginia health systems agency was the first agency in the region to complete its plan. Montgomery County is now completing work on its draft proposal, and the District of Columbia recently began preparations for drafting a plan.