A paper on ways to combat teen-age pregnancy, described in an article Thursday, was submitted to but not delivered at the Child Welfare League national conference.

Offering $2,000 to any teen-age girl on welfare who reaches 20 without having a baby might be a "very cost-effective" and highly controversial way to combat teen pregnancy, but the most effective method has been to make contraceptives available directly to teen-agers in such places as high schools, the Child Welfare League's national conference was told yesterday.

Martha Burt and Freya L. Sonenstein, senior research associates at the Urban Institute, said the $2,000 idea, one alternative outlined at the conference here this week, could be highly effective as a method of preventing teen-age pregnancy. Such pregnancies have increased in recent years until 96 of every 1,000 teen-age girls became pregnant in 1981, the last year for which figures are available. Burt and Sonenstein, however, said in a paper that the payment plan "would almost certainly be considered immoral."

The authors suggested that it may be time to finance a series of demonstration projects to see what works in combating the problem and then use that method.

For example, a program to provide contraceptive services directly to teen-agers in some St. Paul, Minn., high schools "has succeeded in reducing the overall high-school pregnancy rate in schools where it is located by more than 50 percent." Regular followup to reinforce contraceptive use appeared to help.

Classroom sex education and counseling do not seem to have much effect in increasing contraception and reducing pregnancy rates, the authors said. But group sessions with other teens as well as work with grandmothers and parents appeared to offer promise of success.

Other possible strategies cited by the authors at the conference at the Mayflower Hotel included providing child care to enable young mothers to go to school and work so they do not permanently rely on welfare or immediately have more children; "guerrilla theater" sessions for working out problems and concepts; paying youngsters to participate in various programs; and assigning a person to work with a teen-ager not just for sporadic sessions but for continuing supervision and arrangement for services.

The girls most likely to have babies early are those with "histories of school failure, a mother who was a teen parent, whose parent(s) received welfare, and who are poor and nonwhite," the authors said.

The authors said teen mothers are likely to end up on welfare: Studies have found that half the welfare caseload is made up "of households in which the female head had her first baby as a teen-ager."

The league's discussion of ways to reduce teen pregnancy came as the Alan Guttmacher Institute in New York, an affiliate of Planned Parenthood, released a study showing that the 1981 teen-age pregnancy rate in the United States was more than double that for industrialized European countries.

For the United States, the pregnancy rate for teen-agers 15 to 19 was 96 per 1,000 girls. For England and Wales the figure was 45, for Canada 44, for France 43, for Sweden 35 and for Holland 14.

The study attributed the difference in rates to much better programs in the European countries to foster contraception.

The study said the higher U.S. rates are attributable in part to restrictions on teen access to contraception and on teaching about birth control in the schools, in contrast to other countries.

Critics of the contraceptive programs disagree. Many say that providing contraception to young girls encourages sexual activity and undermines moral teachings against promiscuity.

Teen pregnancy has been a problem in the United States for a generation or more. According to the National Center for Health Statistics, in 1981 about two-fifths of all pregnancies among girls aged 15 to 19 ended in induced abortions.

In 1982, pregnancies in girls under 20 resulted in 523,531 live births. Of these, 51.4 percent were to single women. For whites that age, the out-of-wedlock rate was 37 percent, for blacks 87.3 percent.