|04. Micronutrients and Pregnancy Outcome|
Creating offspring is one of mans most cherished achievements and joys. For many it is the main drive for life and the reason to be. Unfortunately this act of procreation is also in many countries the most dangerous period in life. Maternal mortality remains high in many developing countries and pregnancy is beset with high incidences of miscarriages, pre-term deliveries, low birth weight and birth trauma, which endanger the chances of survival of the newborn.
The high associated mortality risk of pregnancy together with a low survival chance of the child makes pregnancy a major investment for many women.
During pregnancy the foetus is entirely dependent on his mother for his growth and development. Her general physical status can therefore profoundly affect the health status of the neonate at birth and so his survival chances. It is long known that a low energy intake during pregnancy affects birth weight. During the winter hunger in Holland (Lumey 1988, Lumey 1992) and the siege of Leningrad (Antonov 1947), at the end of the second world war, food rations decreased considerably. Babies born in that period had a birth weight 338 gr lower than before the famine. However, birth weight was little affected if the food ration stayed above 1500 Kcal per day. These findings led to enthusiastic implementation of supplementary food programs during pregnancy in a wide variety of settings. The results were unfortunately rather disappointing. Birth weight increased on average 50 gr. With a few exceptions where the higher increase in birth weight was probably due to the addition of a mineral supplement. These studies also highlighted the existence of adaptation mechanisms. During pregnancy, metabolic changes occur that protect the mother and her pregnancy through an increased metabolic efficiency. The foetus is also relatively protected at the cost of the nutritional status of the mother (Prentice et al . 1983, Lechtig et al. 1975a, Lechtig et al . 1975b, McDonald et al . 1981, Adair & Pollit 1985, Mora et al . 1979, Mardones-Santander et al . 1988). For micronutrients, similar mechanisms seem to be in place. In a deficiency state of the mother, the foetus will be in part protected with a higher stress on the mother.
Since micronutrient deficiencies can affect maternal morbidity and mortality, and are also essential for foetal development, it is difficult to separate the effect of a deficiency between mother and child. Recent research even suggests that after the period of infancy, the health of the child and even the adult can be influenced by the foetal period. Coronary heart disease, hypertension and type 2 diabetes are thought to originate, in part, from impaired intra-uterine growth and development. These diseases may be a consequence of programming whereby a stimulus or insult at a critical, sensitive period early in life has permanent effects on structure physiology and metabolism (Godfrey & Barker 2000). Maternal mortality is also very difficult to measure and relate to interventions. More proxy indicators on morbidity can give an idea if an effect on mortality can be suspected.
The present review combines therefore the effects of a deficiency on mortality, maternal morbidity and effects on the newborn.