Trends in ages at key reproductive transitions in the United States, 1951–2010

Key sexual and reproductive health events typically mark changing life stages with different reproductive health service needs. Knowing the typical ages at such events helps describe the need for and plan for services. We used five National Surveys of Family Growth, covering interviews conducted from 1982–2010 and allowing us to measure retrospectively from 1951. Men were interviewed starting with the 2002 NSFG, and we supplement with data from the 1995 National Survey of Adolescent Males. Using event history techniques, we apply a cohort approach to examine trends in median ages at key reproductive transitions: menarche, first sex, first contraceptive use, first union, first marriage, first birth, and second birth. Additionally, we use a synthetic cohort approach to estimate time spent in various reproductive stages. Analyses consider differences by gender and race-ethnicity using Kaplan-Meier tests of significance. Women report no change in age at menarche. Age at first sex has increased slightly in recent years after a longer decline for both genders. Time from first sex to first contraceptive use has declined, and varies little for women 15 and older. For the most recent cohorts of women, median age at first birth, is earlier than median age at first marriage. A decrease in the proportion of women with long delays between first and second birth suggests a compression of childbearing. The large majority of the reproductive years are spent sexually active and using contraception. Thus, women have a lengthy period during which they require effective methods, particularly long-acting reversible methods.