The foetus is totally dependent upon the mother for its nutrition.

• The placenta is the protector and mode of nourishment for the developing foetus.

• The transport of different nutrients across the placental barrier is specific to that nutrient

Introduction — 

The foetus is a separate unit from the mother attached by the placenta, an important organ which serves both as a protector of, and source of nourishment for the developing foetus. During the first days following conception and implantation of the fertilised human ovum, nutrition is from local sources. Thereafter the of the foetus is dependent upon nutrition from the mother through the placenta. For the first 4–5 months, placental growth is greater than that of the foetus, but from thereon foetal growth exceeds that of the placenta. By full term at 40 weeks, the weight of foetus, placenta and liquor amni is 5 kg, 3.5 kg of which is the baby and 0.5 kg the placenta.

The placenta is a defined, transporting organ by the fourth week of pregnancy, which not only transports nutrients, but also is a source of oxygen to the foetus. The placenta is the means whereby carbon dioxide and substances excreted by the bowel and kidneys of the foetus are eliminated into the maternal circulation.

It is increasingly appreciated that the health of the baby is a determinate of the well being of the adult. Perhaps the diet of the pregnant mother may be the most important contribution to the health of a population. This is no absolute but well worth noting.

1. The foetus is separated from the mother by the placenta, an important organ which serves as both a protector of and nourishment source of the developing foetus. For the first 4–5 months, placental growth is greater than that of the foetus; thereafter foetal growth exceeds that of the placenta.

2. The placenta is a defined, transporting organ by the fourth week of pregnancy. It not only transports nutrients and is the source of oxygen, but also is the means of excretion via the bowel and kidneys and route of elimination of carbon dioxide.

3. Glucose is an important foetal and placental fuel. The transfer system is stereospecific, can be saturated, and is a mediated process.

4. Amino acid transport across the placental membrane involves mediated transport mechanisms through both the microvilli and the basal membrane.

5. There is metabolism of glucose within the placenta, producing lactate at a high rate.

6. Lipoprotein lipase on the maternal surface of the placental membrane hydrolyses triacylglycerol carried by maternal VLDL. The free fatty acids are taken up and may be used by the trophoblast or transferred to the foetus. The foetus is dependent on the placental transfer of substrates from the mother; these can then be used for lipid synthesis.

7. Much of the essential fatty acids required during the perinatal period are for brain growth. Of these, 50% are long-chain polyunsaturated fats (PUFA). The maximum rate of brain development in humans is in late gestation and in the early postnatal period.

8. Phospholipids comprise 25% of the brain’s solid matter and are important for brain function. There appears to be no blood-brain barrier to fatty acid transfer in the infant or foetus. Variations in composition of dietary PUFAs may lead to different concentrations of long-term PUFAs in brain tissue.

9. Water- and lipid-soluble vitamins and inorganic nutrients are transported across the placenta by specific transport systems

Further Reading — 

Battaglia, EC. and Meschia, G. (1988) Foetal nutrition. Annual Review of Nutrition, 8, 43–61.

Farquharson, J., Cockburn F., Patrick,W.A.,Jamieson, E.C. and Logan, R.W (1992) Infant cerebral cortex phospholipid fatty-acid composition and diet.British Medical Journal, 340, 810–13.

Hay W ( 1999) Nutrition-gene interactions during intrauterine life and lactation. Nutrition Reviews 57, S20-S30

Zaret, K.S. (1996) Molecular genetics of early liver development. Annual Review of Physiology, 58, 231–52.