According to Key findings from NCHS and the Center for Disease control (CDC), the average age of first-time mothers increased 3.6 years from 1970 to 2006, from 21.4 to 25.0 years. Increases in average age at first birth were more pronounced in the 1970s and 1980s.
Why does age matter? The CDC says that age at first birth influences the total number of births that a woman might have in her life, which impacts the size, composition, and future growth of the population. And, of course, the age of the mother plays a factor in a wide range of birth outcomes (e.g., birthweight, multiple births, and birth defects).
From 1970 to 2006 the proportion of first births to women aged 35 years and over increased nearly eight times. In 2006, about 1 out of 12 first births were to women aged 35 years and over compared with 1 out of 100 in 1970.
In 2005, the New England Journal of Medicine, published and article stating that the number of first births per 1,000 women 35 to 39 years of age increased by 36 percent between 1991 and 2001, and the rate among women 40 to 44 years of age increased by a remarkable 70 percent. Additionally, in 2002, 263 births were reported in women between 50 and 54 years of age.
According to NCHS, several factors may account for the delay in childbearing, most importantly educational opportunities and career choices for women. From 1970 to 2000 the number of women completing college has nearly doubled and the number in the labor force has gone up by almost 40 percent. Changes in contraception use, economic cycles, social support, and marriage patterns should also be considered. .