Age at first birth and family size: evidence from a longitudinal study.

Abstract

The relationship of age at 1st birth and subsequent fertility was examined by introducing into the analysis some measures of orientation toward family roles not usually available in other studies. The data source was a longitudinal study spanning the 1962-77 period. The sample drawn from 1961 birth and marriage registrations constitutes a probability sample of all white women in the Detroit metropolitan area who had just married or who had just had a 1st 2nd or 4th birth. 5 interviews were completed during this period. Excellent response rates were obtained throughout the study with 1157 women constituting 89% of the original sample still participating in 1977. The findings confirmed the expected negative association between age at 1st birth and completed family size. For the sample as a whole the average number of children ever born in 1977 declined monotonically with age at 1st birth. Within separate parity groups the relationship of fertility to age at 1st birth was not as strong and somewhat less regular but a monotonic inverse relationship again appeared within parity groups (with 1 minor exception) when respondentss background (wifes education religion and number of siblings; respondents fathers education and occupation) were controlled. Of the background variables wifes religion exerted the strongest effect on the relationship between fertility and age at 1st birth. Catholic women had larger families than other women and also married at older ages. Work experience between marriage and 1962 including current work was associated positively with age at 1st birth. The differentials in the proportion with some work since marriage associated with age at 1st birth were sizable and the differences were statistically significant for parities 0 1 and 2. The combined index of sex role attitudes had no regular relationship to age at 1st birth. Women who were very young at 1st birth (under age 20) in every parity group did express more traditional attitudes but there were no attitudinal differentials associated with later ages at 1st birth. When the 3 role orientation variables were added to the regression analysis they had no effect on the age at 1st birth/fertility relationship beyond that accounted for by the background variables. Neither home oriented behavior nor traditional sex role attitudes accounted for the higher fertility of women who had their 1st birth at an early age. Women who had an early 1st birth went on to have larger families than women who postponed childbearing longer.