[Changes in fertility]. / Cambios en la fecundidad.

PIP: Mexican fertility levels did not change dramatically in the years 1988-97, but maintained a gradual downward trend. In the late 1960s and the entire decade of the 1970s, the fertility decline was spectacular. National fertility surveys beginning in 1976 have provided rich information on fertility trends and their determinants, which along with census data reveal the history of the past 3 decades of fertility change. The 1995 total fertility rate of 2.9 was less than one-half of the 1965 total fertility rate of 7.1. The age pattern of fertility has also changed, with the proportion of births to younger mothers progressively increasing. The average age at childbirth declined from 29.2 in 1965 to 27.4 in 1995. The 1995 age-specific fertility rate for women over 35 was one-fourth that of 1965. Sterilization is the most widely used contraceptive method among women over 30, and, at present, 70% of women over 35 are sterilized. The decline in adolescent fertility is due primarily to the rise in average age at first marriage. The marital fertility rate among women 15-19 years old remains at about 400/1000, a high level explained by the frequency of marriages to legitimize prenuptial conceptions. Comparison of fertility data for 5-year periods shows the impact of contraceptive usage and of the family planning program, especially during 1975-80, when the public family planning program was most active. The age pattern of fertility decline suggests that women used contraception more to limit than to space fertility. Fluctuations in fertility after 1980 appear to be linked to the relaxation of public sector family planning activities. The average number of children born by age 40 declined from 5.68 for women born in 1941-45 to 3.46 for those born in 1955-60.^ieng