Chapter 3: Prenatal Development This chapter begins with a discussion of motivations for parenthood and current changes in birth patterns. Today, men and women are more likely to weigh the pros and cons of having children than they did in previous generations. The American family has declined in size over time, a trend that has child-rearing benefits. Births to women over thirty have increased, a change associated with both advantages and disadvantages for children. At no other time is change as rapid as it is before birth. Prenatal development takes place in three phases: (1) the period of the zygote, during which the newly fertilized ovum travels down the fallopian tube and attaches itself to the uterine wall; (2) the period of the embryo, during which the groundwork for all body structures is laid down; and (3) the period of the fetus, the "growth and finishing" phase. The prenatal period is a vulnerable time. Teratogens such as drugs, smoking, alcohol, radiation, environmental pollution, maternal disease, inadequate nutrition, maternal stress, and Rh blood incompatibility can damage the developing organism. Prenatal health care is vitally important to ensure the health of mother and baby. For most expectant parents, the prenatal period is not a time of medical hazard. Instead, it is a time of major life change in which mothers and fathers prepare for parenthood. ab_webmaster@abacon.com ©2001 Allyn & Bacon