The patterns of childbearing in the United States have been changing in recent years along with the general demographic picture of the country, and the seasonality of childbearing throughout the life cycle has been shifting because of a number of forces. One of these is the aging of the population, coupled with major shifts in the emphasis women place on careers. The entire pattern of family structure in the U.S. has been in a state of flux as divorce rates increase, out-of-wedlock births increase, and patterns of work change as both husband and wife tend more and more to work outside the home, altering the timing of births and birth decisions for families. In the past, the seasonality of childbearing was more stable and clearly delineated, with women of a certain age marrying and starting families as a matter of course. Today, the birth rate for that particular pool of women has decreased somewhat while there have been increases on either side of the age group, increases in the incidence of pregnancy among teenage girls (and in the number of such girls carrying their children to term and even keeping the babies when they can) and among older women who have made career choices to defer childbearing and who are trying to catch up in the face of their "biological clock," or the likelihood that they will reach an age at which childbearing is inadvisable if not impossible.
The American family has changed in a number of ways over the course of this century and has adapted to such environmental factors as evolving technologies, economic conditions, and social trends. These trends were especially pronounced in the 1960s and into the 1970s as the so-called baby-boom generation of children born immediately after World War II came of age. The last quarter of a century has been marked by the deterioration of the traditional nuclear family unit. There is no such thing as a "typical" family, for family experiences are varied and variabl...