Pregnant women must eat for two

False. This piece of folk wisdom has been proved wrong. The most important nutritional consideration in relation to pregnancy is to enter it with good nutrient reserves and preferably no more than 10 per cent under or 20 per rent over desirable body weight for height.

During the first three months (the first trimester) of pregnancy, health authorities recommend no increases in food or nutrient intake. For the second and third trimesters increases in the intake of energy (8 to 13 per cent), protein (11 per cent), B-group vitamins (10 to 12 per cent, except for B-12 which should be increased from 2 to 3 micrograms per day and for total folacin which should be increased from 200 to 400 microgram per day), vitamin C (200 per cent), calcium (60 to 130 per cent), iron (at least 25 per cent or, controversially, much more), zinc (about 30 per cent), and iodine (13 per cent) (see Appendix 2 for Recommended Daily Nutrient Intakes). In general, food intake does not need to be twice as great. Indeed, with recommendations for increases in energy intake being much less than increases for certain essential nutrients, the nutritional quality of the diet must improve. There is some doubt that energy intake needs to be increased at all, since it is apparently possible for pregnant women to cut back their energy expenditure according to the needs of the foetus.

The reason there is controversy about recommendations for increases for iron during pregnancy is that, although iron deficiency occurs commonly during pregnancy, it would be less common if good iron stores were in place at conception. It seems surprising, although often necessary, that pregnant women should need to take iron supplements in order to meet their day-to-day iron requirements, rather than receive all the iron they need in their food.

What is also clear is that good nutrition during pregnancy should not be compromised by cigarette smoking, which leads to underweight babies, or by alcohol consumption, which can adversely affect foetal mental and physical development. There is no safe level of cigarette smoking. For alcohol a little may not be harmful, but no alcohol is preferable.