Maternal nutrition and metabolic control of pregnancy

A successful human pregnancy follows a chancy path from fertilization to implantation, through an extended period of placental and fetal growth, to a period of fetal organ maturation that corresponds to a change from uterine quiescence to coordinated uterine contractions, and finally to cervical dilation and parturition. The fate of a fertilized human ovum is far from secure (Figure 3.1). It is estimated that one-third to one-half of human conceptuses either do not implant or are lost shortly after implantation. Among those fertilized ova that successfully implant, as many as one in five succumb before delivery. Even in developed nations, of those fetuses that are delivered, 10% are preterm, 5% are small for their gestational age, and 3% have one or more severe congenital defects (Keen et al., 2003). A significant proportion of human morbidity and mortality, from neonates to adults, may be attributable to events in utero. Preterm birth and intrauterine growth restriction (IUGR) are significant sources of neonatal morbidity and mortality. In 1947, Eastman (1947) declared, ‘Only when the factors underlying prematurity are completely understood can any intelligent attempt at prevention be made.’ After considerable research effort since then, our understanding of the causes of preterm labor still is far from complete, and the rate of premature labor and birth has not declined (Goldenberg et al., 2003).