ONE explanation for the contraceptive revolution that has swept the world since the 1960s is that scores of governments and millions of couples suddenly concluded that smaller families would mean greater prosperity.
It was a conclusion that prompted most developing countries to offer family-planning services and a majority of couples to accept them. The result: a lower rate of population growth worldwide.
Figuring out how to bridge the gap between slower growth and no-growth - the goal of the United Nations population conference now in its third day in Cairo - is likely to be harder. (The view from Mexico, Page 9.)
The main em-phasis will be on empowering women. But the focus will also be on their younger sisters, the millions of teenage girls who give birth every year because they have largely been ignored by family-planning agencies.
``Meeting the needs of adolescents is one of the next frontiers in meeting the global population challenge,'' notes Herbert Friedman, head of the Geneva-based World Health Organization (WHO) adolescent-health division.
Adolescent sex education is one controversial issue - others include abortion and reproductive rights - remaining after preliminary meetings to the Cairo conference. These issues were ``bracketed'' for further discussion because of objections from the Vatican. And on Sept. 6, the Vatican issued a new condemnation of the proposals.
The job of working out compromise language has been assigned to a ``main committee'' comprising two delegates from each of the 177 countries represented at the conference. The Vatican is weighing a compromise on the most controversial issue that would move references to abortion out of the section on family planning in the 113-page draft ``Program for Action'' and specify that abortion is not a human right.
``The Holy See cannot give explicit or implicit support to those parts of the [draft] document regarding abortion,'' a ``weakening'' of the definition of the family, or provisions to provide adolescents with confidential sexual health care, papal spokesman Joaquin Navarro said Sept. 6. A senior conference official was more optimistic, predicting that a ``balance between parental rights and the important needs of adolescents'' would eventually be struck.
Experts here say providing information about sexuality and reproduction to the world's more than one-half-billion teenagers has crucial health implications, especially in an era of AIDS. But the extended abstinence or more-protected sexual activity that often results from such education has demographic implications as well, since adolescents account for a higher proportion of total births worldwide each year.
The raw statistics on adolescent sexual activity are striking. Between one-fifth and one-half of all unmarried teenagers in developing countries are sexually active, according to the Worldwatch Institute. Of all 14-year-old girls alive today, 40 percent will be pregnant by the time they are 20. In some Asian and African countries, teenagers below the age of 18 account for half of all pregnancies, according to the UN.
Though differences exist between married and unmarried teenagers, there is one common denominator: Nearly all remain largely untouched by the global reach of family planning, leaving them vulnerable to unwanted pregnancies and higher-risk pregnancies. Young women between 15 and 19 account for up to a fifth of all induced abortions worldwide.
``Adult women are having fewer pregnancies and adolescents are not,'' says a UN official, referring to one consequence of family-planning agencies having had far greater success reaching older married women.
Conservative Roman Catholics and Muslims say a provision calling for expanded sex education in the draft plan of action now being debated in Cairo will encourage adolescents to have premarital sex.
BUT a 1993 WHO review of 19 recent studies suggests that it would result in delayed sexual activity and lead to more contraceptive use - both of which will delay childbearing and lengthen the time span between generations. ``One of the greatest myths in the world is that giving information to young people results in promiscuity,'' Dr. Friedman says.
Experts say sex education is most effective when taught at home or imparted by peers. Worldwide, governments and organizations have tried techniques from setting up clinics that exclusively serve adolescents to promoting counseling sessions that, says a Polish pediatrician at the conference, have taught teenagers ``how to delay, how to say no, and how to have enough self-esteem to risk criticism for saying no.''
The spread of AIDS also makes a compelling point to adolescents. ``Kids see their parents and friends dying, and they get educated in a hurry,'' says Margaret Nagita. ``When you put AIDS and education together, people really change their behavior.''