affected by many factors. These include edema during pregnancy and the route of delivery (Dennis and Bytheway, 1965); prepregnancy weight, postpartum weight, parity, and maternal age (Brewer et al., 1989); and weight gained during pregnancy (Greene et al., 1988).
There is a need for research to develop indicators of nutritional status, analogous to those for weight gain during pregnancy, that make use of either the pattern or the total magnitude of the changes. Further research is also needed to investigate the use of other anthropometric indicators (e.g., various skinfold thicknesses or circumference measurements) for assessing the nutritional status of lactating women. Other approaches (e.g., bioelectrical impedance or isotope dilution [Wong et al., 1989]) for the evaluation of changes in body composition also merit study in lactating women.
Table 4-1 provides the biochemical measures of nutritional status from the few studies that have been conducted in lactating women and compares them with values for nonpregnant, nonlactating women. Also included are compiled values from presumably well-nourished lactating women living in industrialized countries. It is evident from Table 4-1 that data on a variety of biochemical measures of nutritional status have been collected for lactating women, but that the sample sizes range from only 3 to 36. Where comparison was possible, there was remarkably little difference between values for lactating women and those for nonpregnant, nonlactating women.
The blood lipid profiles of lactating women at 6 weeks post partum have been compared with those of parturient women who were not lactating (Knopp et al., 1985). The lactating women maintained lower total triglyceride and higher total cholesterol values than those in the nonlactating group. There also were statistically significant differences between the two groups in values for various lipoprotein lipids and apoproteins (Table 4-2). In contrast, both plasma cholesterol and triglyceride concentrations were higher at 8 weeks post partum than they were before conception among 14 lactating Swedish women (Fåhraeus et al., 1985). These studies suggest that lactation causes changes in lipoprotein metabolism.
Table 4-3 provides anthropometric measurements of nutritional status for lactating women and for nonpregnant, nonlactating women in the United States.