The Roman Catholic archbishop of Washington has issued a statement reaffirming the Catholic church's longstanding opposition to artificial contraception and urging Catholics to "study the facts" about natural family planning.

Archbishop James A. Hickey's letter, sent to some 700 priests and lay leaders in the archdiocese, came in the wake of news reports, which Hickey said were misleading, of discussions of birth control at the worldwide Synod of Bishops now under way at the Vatican.

Archbishop John Quinn, head of the American Catholic hierarchy, told the synod Monday that "a very large number of men and women of good will do not accept the [church's] teaching" on the evils of contraception. He reported that studies show that 76.5 percent of Catholic women in this country use contraception.

In raising the issue at the synod, which is considering questions of family life, Quinn made it clear that he and other members of the Catholic hierarchy fully accept Humanae Vitae [the 1968 papal encyclical on birth control] at the "authentic teaching of the church."

Quinn called on the Vatican to "initiate a formal dialogue with Catholic theollgians" to get them to help persuade Catholics to live by the church's teaching on birth control. He said they should not do it by placing the doctrine "in the context of a developed teaching on responsible parenthood."

In his letter, Hickey urged Catholics to reread the 1968 encyclical, which he called "a prophetic document." He emphasized that the document "is above all, a positive presentation of marriage and its mission of love and life in view of our natural and supernatural vocation in Christ."

The encyclical, issued by Pope Paul VI, upheld traditional Catholic bans on any form of artificial contraception. It was issued after an international Vatican study commission recommended that the church accept artificial contraception.

Hickey also urged Catholics to "study facts regarding natural family planning. It presents a way," he said, "that is both effective and moral in achieving truly responsible parenthood."

In natural family planning, which Hickey said is "something quite different from what was once known as 'the rhythm method,'" a woman determines when she is fertile by observing her vaginal secretions or taking her temperature. During the time when she is likely to conceive, the couple must abstain from intercourse. Though they all require abstinence, these new methods are considered to be much more effective than the rhythm method, which relies primarily on the calendar to determine fertile periods.