The marital status of American women at the time of their first births has significantly changed since the 1930s. In the early 1930s, one in six first births to women under age 30 was conceived or born before marriage, compared with one in two births in the early 1990s. The proportion of first births among teenage women resulting from premarital conceptions tripled from 28 percent in 1930-34 to 89 percent in 1990-94. This proportion increased more as a result of an increase in the proportion of births that were premaritally born than an increase in the proportion of births that were premaritally conceived.