Changes in marriage age and first birth interval in Huaning County, Yunnan Province, PR China.

The timing of marriages, first birth interval and the prevalence of premarital conception (PMC) among women of successive birth cohorts in one rural county in Yunnan, China, were examined. Detailed pregnancy histories were collected for 1,336 women aged 15-64 years using a Life History Calendar. The rising marriage age and shorter first birth interval correspond to over-all changes in the Chinese society over the same time period. The mean age at first marriage for women born before 1950 was just below 20, and 22.5 among women born 1976-1980. The later marriage age was partly offset by the dramatic shortening of the first birth interval from over 30 months in the oldest cohort to 11-12 months in the youngest. One explanation of the shortening of the first birth interval may be the increase in premarital conception. Among the young women in our study almost one-third of first pregnancies were conceived before marriage.