ABSTRACT
During development the fetus is exposed to two major categories of influence. First there is the set of genetic instructions encoded in the nucleus. This program for development, collectively called nature, is then modified by the effects of surrounding environmental influences on the embryo and the fetus. Collectively these environmental influences are called nurture. In the last 15 years, it has become clear that one major aspect of the environment that influences fetal behavioral development is the level and pattern of contractility of the myometrium. This influence has been most extensively investigated in late gestation, and this review covers investigations conducted in the last third of pregnancy. Myometrial activity does affect uterine blood flow, and it is likely that there may be effects of myometrial activity on the developing embryo and early fetus. The potential effects of myometrial activity on the fetus during these early periods of development have not been studied. The metabolic demands of the early embryo and early fetus are not as great as those of the late, near-term fetus, and therefore, small changes in oxygen and nutrient delivery may not exert as major effects on fetal development in early pregnancy as they have the potential to exert in late pregnancy. Firm information on the possible effect of myometrial activity in early pregnancy awaits appropriately designed experiments. The purpose of this chapter is to review the effects of myometrial activity on fetal neurophysiological, neuroendocrinological, and behavioral development during the last third of pregnancy.
