Zelnik M, Kim Y J, Kantner J F
Fam Plann Perspect. 1979 May-Jun;11(3):177-83.
One in five U.S. females have had intercourse by age 16, and two-thirds, by age 19. Almost all the experience is premarital. One in 10 U.S. women get pregnant before age 17; one-quarter before they are 19, and eight in 10 of these pregnancies are premarital. More than one-third of those who are sexually active premaritally have a premarital pregnancy before they turn 19, one-quarter by the time they are 17.
五分之一的美国女性在16岁时已有过性行为，三分之二则在19岁时已有过性行为。几乎所有这些经历都是婚前的。十分之一的美国女性在17岁前怀孕；四分之一在19岁前怀孕，其中十分之八的怀孕是婚前的。超过三分之一婚前有性行为的人在19岁前有过婚前怀孕，四分之一在17岁时就有过。
