The risk of premarital first pregnancy among metropolitan-area teenagers: 1976 and 1979.

Among sexually active teenage women living in metropolitan areas of the United States, the risk of premarital pregnancy within two years of first sexual intercourse rose from 32 percent in 1976 to 36 percent in 1979. As of 1979, 33 percent of unmarried white teenagers, and 43 percent of unmarried black teenagers, had conceived within 24 months of becoming sexually active. The increase in pregnancy risk between 1976 and 1979 was relatively greater for whites than for blacks at three, six and 12 months after first intercourse. The reverse was true at later intervals. The risk of pregnancy is disproportionately concentrated in the early months of sexual activity. Forty-five percent of all premarital pregnancies among those interviewed in 1979 had been conceived within the first six months of sexual activity, and 36 percent had been conceived within three months. In 1976, 27 percent of teenagers who had become sexually active before the age of 15 were premaritally pregnant within two years. By 1979, this proportion had risen to 41 percent--a 52 percent increase in the risk that accounts for almost all of the total three-year increase in premarital pregnancies among sexually active teenagers. The most pronounced increase in risk of pregnancy was registered among whites who became sexually active when they were younger than 15. Their 24-month probability of conception rose from 20 percent in 1976 to 39 percent by 1979. Levels of risk for unwed teenagers who initiated intercourse at ages 15-19 increased relatively little.(ABSTRACT TRUNCATED AT 250 WORDS)