7
Conclusions and Recommendations

CONCLUSIONS

  1. Our knowledge of the metabolic adjustments that occur during human pregnancy are insufficient to establish energy requirements during pregnancy and lactation under different conditions of energy and other nutrient intake, body composition, physical activity, work position, etc. Similarly, we know very little about how such metabolic adjustments (and their limits) may affect pregnancy or lactation outcomes under these various conditions.

  2. Epidemiologic studies, mostly from developing countries, strongly suggest that women who are underweight before pregnancy and who have insufficient energy intakes during pregnancy are at higher risk of delivering growth-retarded infants. Improving the nutrition of women during pregnancy and lactation reduces the risk of intrauterine growth retardation and may improve lactation performance. These effects occur without apparent change in physical activity and have been interpreted as being due to improvement in energy balance, although such an interpretation may be overly simplistic. The effect of such nutritional improvement on other maternal (mortality, postpartum health, and nutritional status) and fetal/child (spontaneous abortion, congenital anomalies, and morbidity) outcomes is difficult to evaluate from the available evidence.

  3. Studies from both developed and developing country settings suggest that strenuous physical activity may adversely affect energy balance in



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OCR for page 187
Nutrition Issues in Developing Countries: Part I: Diarrheal Diseases - Part II: Diet and Activity During Pregnancy and Lactation 7 Conclusions and Recommendations CONCLUSIONS Our knowledge of the metabolic adjustments that occur during human pregnancy are insufficient to establish energy requirements during pregnancy and lactation under different conditions of energy and other nutrient intake, body composition, physical activity, work position, etc. Similarly, we know very little about how such metabolic adjustments (and their limits) may affect pregnancy or lactation outcomes under these various conditions. Epidemiologic studies, mostly from developing countries, strongly suggest that women who are underweight before pregnancy and who have insufficient energy intakes during pregnancy are at higher risk of delivering growth-retarded infants. Improving the nutrition of women during pregnancy and lactation reduces the risk of intrauterine growth retardation and may improve lactation performance. These effects occur without apparent change in physical activity and have been interpreted as being due to improvement in energy balance, although such an interpretation may be overly simplistic. The effect of such nutritional improvement on other maternal (mortality, postpartum health, and nutritional status) and fetal/child (spontaneous abortion, congenital anomalies, and morbidity) outcomes is difficult to evaluate from the available evidence. Studies from both developed and developing country settings suggest that strenuous physical activity may adversely affect energy balance in

OCR for page 187
Nutrition Issues in Developing Countries: Part I: Diarrheal Diseases - Part II: Diet and Activity During Pregnancy and Lactation women with low prepregnancy weight-for-height and thereby impair fetal growth in women who already are undernourished before or during pregnancy. Despite a large number of studies, the effects of work conditions, activity patterns, and physical exercise on other outcomes of pregnancy and lactation are unclear. Although many observational studies from developed countries suggest that strenuous exercise or fatiguing work in the third trimester may increase the risk of preterm delivery, the findings have not been consistent. Moreover, their relevance for working women in developing country settings is unclear. Gestational weight gain reflects, in part, a balance between energy intake and expenditure. The epidemiologic evidence is very strong that low weight gain increases the risk of intrauterine growth retardation, especially in women with low prepregancy weight-for-height. Several studies suggest a similar increased risk for preterm delivery, but methodologic problems with these studies do not permit firm inferences. RECOMMENDATIONS The foremost recommendation is for more research related to nutrition, physical activity, and reproductive performance of pregnant women in different ecological settings. Greater efforts should be made to examine effects on outcomes beyond fetal growth and gestational duration, including lactation performance; maternal outcomes of pregnancy (e.g., complications of delivery, duration of labor, gestational hypertension and pre-eclampsia, and subsequent health and nutrition status); and neonatal mortality, morbidity, growth, and functional performance. To provide useful information for clinical and public health intervention, future studies should attempt to isolate the effects of diet and physical activity, as well as measure any tendency for their interaction (i.e., synergistic effects). Similar studies should be undertaken in animals, focusing on possible physiological mechanisms by which diet and physical activity may affect fetal growth, uterine contractile activity, and mammary gland function. Studies are needed on lactation physiology, particularly on those aspects that are expected to be influenced by interactions between physical activity and nutritional status. Effects on milk composition,

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Nutrition Issues in Developing Countries: Part I: Diarrheal Diseases - Part II: Diet and Activity During Pregnancy and Lactation milk volume, duration of lactation, and maternal abilities to respond to changing demands of infants and the short-and long-term effects of lactation on maternal health merit special attention. Studies are needed to document the conditions of work, the required physical activity of women during pregnancy and lactation, and the economics and sociology of work among specific population groups and ecological conditions. The effects of urbanization on the working patterns of women during pregnancy and lactation requires documentation. Measurements are needed of the energy requirements of common activities in specific ecological settings. Studies are needed of the metabolic adjustments that occur during pregnancy under different ecological conditions. At present, in spite of the meager evidence at hand, it appears reasonable to promote programs that attempt to reduce energy expenditure and improve nutrition in pregnant and lactating women. These programs should complement, rather than replace, existing nutritional and prenatal and postnatal care programs designed to improve the health and nutrition of women of reproductive age before, during, and after pregnancy and lactation. These programs should be an integral part of efforts to improve the social and economic status of women in developing countries.