The worldwide synod of Roman Catholic bishops reemphasized the church's traditional sexual code yesterday, dashing the hopes of a large portion of the church's membership for some modification of prohibitions against artificial birth control and divorce.

On the last day of their month-long synod in Rome, the bishops issued a 2,700-word "Message to Christian Families in the Modern World." It asserted that "the transmission of life is inseparable from the conjugal union" and that "the conjugal act itself . . . must be fully human, total, exclusive and open to new life."

The message also reaffirmed church teaching on divorce, sterilization and a range of other issues involving family life.

Pope John Paul II, acknowledging the bishops' message during a closing mass at the Sistine Chapel yesterday, said that Catholics who have remarried after a divorce "can and ought to participate" in some aspects of church life, but that they cannot receive communion unless they abstain from sexual relations in their second marriage.

"By virtue of their baptism $ can and ought to participate in the life of the church by praying, by hearing the word, by assisting at the eucharistic celebration of the community and by fostering charity and justice," the pope said.

But they cannot be readmitted to the sacraments, he continued, unless they "live in a manner which is not opposed to the indissolubility of marriage" by living "in complete continence, that is, by abstinence from acts in which only married couples can engage." Since the Catholic Church does not recognize divorce, it does not consider remarriage after divorce to be valid.

In their message, the bishops strongly supported the basic equality of men and women. The statement said that "the essential equality and complementarity of the sexes" is a part of "Gods plan" in marriage.

"Husband and wife are certainly different, but they are also equal. The difference should be respected but never used to justify the domination of one by the other. In collaboration with society, the church must effectively affirm and defend the dignity and rights of women," the message said.

The statement did not deal with the controversial question of how equality of the sexes applies to the role of men and women in the structure of the church.

During their deliberations, the issue of birth control dominated the discussions among the 216 bishops who gathered from throughout the world to discuss the state of the family.

It was the major theme that was discussed," said Archbishop Joseph N. MacNeal, president of the Canadian bishops' conference.

Very eary in the sessions, Archbishop John Quinn of San Francisco, who is president of the U.S. bishops' conference, told the synod that some polls have indicated that nearly 80 percent of U.S. Catholics ignore the church ban on artificial contraception. While maintaining that he upheld the teachings of Pope Paul VI's 1968 encyclical, Humanae Vitae, which condemns all so-called artificial means of contraception, the American prelate urged a long-range study of the question.

There were reportedly numerous calls in the closed-door sessions of the synod for the church to undertake a detailed and broadly based study of the whole area of human sexuality. Whether this emerged in the 43 propositions and recommendations that the synod sent to the pope at the conclusion of its session was not made public.

The bishops' synod is an outgrowth of the Second Vatican Council's call for "collegiality" -- sharing between bishops and the pope in the running of the church. The synod has no power by itself to change doctrine, but the recommendations to the pontiff could have a significant influence, particularly since Pope John Paul, while still a cardinal in Poland, but urged that bishops of the church play a larger role in church decision-making.

In their message, the bishops sharply criticized "certain governments and some international organizations" that they said "do violence to families" by violating "the integrity of the home" and parental rights. The statement proposed an international "charter of family rights" to prevent the use of "such immoral means for the solution of social, economic, and demographic problems as contraception or, even worse, sterilization, abortion and euthanasia."

The message maintained that "the number of families who consciously want to live the life of the gospel . . . continues to grow in all our lands." But even for those who "because of human weakness" fall short of the church's decrees, "there is no reason for discouragement," the bishops said.

"In no way do we ignore the very difficult and trying situation of the many Christian couples who, although they sincerely want to observe the moral norms taught by the church, find themselves unequal to the task because of weakness in the face of difficulties," the bishops said. Such couples, they assert, "need to grow in appreciation of the importance of Christ's teachings and his grace and to live by them" with the aid and encouragement of "the whole church."