Ventura pointed to the government's 1995 national survey of families that found increased use of condoms.

Among black women ages 20 to 24, condom use tripled between 1988 and 1995. In addition, women were more likely to use long-lasting methods such as Norplant, a contraceptive implanted in the arm, and Depo Provera, a birth control injection.

Other explanations are harder to come by, said Moore. Citing the 1995 government survey, she said nearly three in four pregnancies of black women are unintended - including married and single women. Overall, 60.4 percent of unintended pregnancies ended in abortion.

For white women, 43 percent of pregnancies were unintended, she said.

The report's most striking statistic may be the sharp increase in triplets, quadruplets and larger births, which saw the largest jump in a single year since 1971, when the government began keeping these statistics.

The rate has doubled since 1990, quadrupled since 1980 and is five times higher than it was in 1971, when just over 1,000 babies came into the world with at least two companions, the report found.

About a third of the rise is due to an increasing number of older women having babies, who are more likely to have multiple births, Martin said. The rest is due to increased popularity of fertility treatments. About 20 percent of women undergoing fertility therapy have multiple births.

That's a mixed blessing. Babies from multiple births are more likely to be underweight and premature. That often leads to vision and hearing impairments, mental retardation, developmental delays and even death.