Study aspects of delayed child-bearing with the aid of theory-based, empirically tractable models of cohort fertility by birth order. Develop and test models for cohort age distributions of first birth frequencies and estimators for the models, and model the effect of period fertility on cohort first birth fertility. This work would evaluate the Coale-McNeil marriage model as applied to first births. Subsequently, analyze and compare first birth fertility patterns of cohorts of white and non-white women in the U.S., using National Center for Health Statistics (NCHS) data; study the determinants (and trends in the determinants) of delayed child-bearing using fertility and socio-economic variables from the National Survey of Family Growth (NSFG) for 1973 and 1976, and compare delayed child-bearing in the U.S. with that in other developed nations.