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The Effect of Nutrition on Fetal Growth and Development

  Even it is difficult to determine the mean fetal growth curve in the human species, fetal growth curves used in clinical practice are based on data obtained from liveborn infants of different gestational ages. There are two ways of looking at the growth rate. Most commonly, this is considered in absolute terms, change in weight per unit time. During the embryonic and fetal stages, this rate is very slow and then rises to reach a maxium at about the 36th week of gestation, whereupon it declines as term approaches. The second way is to consider relative growth rate, change in weight per unit weight with time. In this manner growth velocity is related to body size.   Body composition during fetal life is also changed. Fat-free weight increases progressively save for a slight deceleration in the final weeks. Protein and fat contents are roughly parallel. Body fat content in late fetal life is increased. It is shown that birth weight is correlated with skinfold thickness.   Placenta acts to transport substances between the tissues of the mother and those of the embryo. The placenta, in combination with the fetal membranes is responsible for the protection, nutrition, respiration, and excretion of the embryo and fetus. At parturition, the fetal membranes and the placenta are separated from the uterus and are expelled.   That fetal growth seems to be unrelated to maternal energy reserves and to depend mainly on the mother"s ability to provide oxygen is in agreement with the idea of the fetus being a perfect nutritional parasite. In contrast, when there is maternal fasting and when the mother becomes hypoglycemic, there is a depression of cardiovascular function and the fetus is victimized.