The Declining Significance of First-Birth Timing

Abstract

A rationale for the hypothesis that the impact of 1st-birth timing on the pace at which 2nd births occur declined for women married between 1950-69 is presented. The hypothesis is tested with proportional hazards models and data from the 1973 National Survey of Family Growth. Results support the hypothesis for white women but not for black. Most of the decline in the impact of 1st birth timing for whites arises from slower 2nd birth timing among women with a rapidly paced 1st-birth while women who delayed a 1st birth experience a reasonably uniform delay to 2nd birth over the period. The survey is a multi-stage area-probability cross-sectional sample of households and includes about 9800 women aged 15-44 who were ever-married or who had children of their own living in the household. The life table results show that for all whites it took 19 months for 25% of the mothers to have a 2nd birth 30 months for 50% and nearly 4 years before 3/4 had a 2nd birth. For all blacks the respective figures are 16 27 and 57 months. Women who delayed their 1st birth 18 months or longer took much longer to have a 2nd birth. Using the proportional hazards methodology both 1st birth timing and marriage cohort have a significant impact on 2nd birth timing among black women but there was no statistically significant interaction between these predictor variables. Efforts should be directed toward explaining why blacks and whites differ with respect to the declining significance of 1st birth timing. The declining influence of 1st birth timing among white women can largely be attributed to slower 2nd birth timing among women with shorter 1st birth intervals. Since only 4 marriage cohorts of whites were examined the results should be interpreted cautiously. Additionally the findings are restricted to women married by age 25. The childspacing patterns of women marrying later may be different. The decline in the importance of 1st birth timing predicting 2nd birth timing may have significant consequences. A rapidly paced 1st birth may not have the same negative socioeconomic consequences as in the past. 1st birth timing may have less impact on life-course events other than fertility. Since 1st birth timing may no longer predict 2nd birth timing to a great extent and expanded search for factors associated with the pace of 2nd births is in order.