The complex processes that occur during pregnancy require a rich supply of protein, vitamins and minerals for both mother and child. If you've built up good stores of nutrients in the months and years before conception through a healthy, balanced diet, the added demands of pregnancy can be met with modest adjustments. If, however, your nutrient stores are low, you run a greater risk of diet-related problems during pregnancy, such as anaemia.

But while your need for certain nutrients does increase during pregnancy, the old adage 'eating for two' doesn't necessarily mean you should eat twice as much food, for a number of reasons:

	Your growing baby isn't as big as an adult.
	During pregnancy, your body becomes more efficient at absorbing nutrients in the digestive system.
	Your body also doesn't excrete nutrients - instead, it builds up stores of vitamins and minerals.

It's the quality of your diet that's important, not the quantity.

The theoretical energy cost of pregnancy has been estimated to be 80,000 calories, but there's no need to increase your overall energy intake until the last trimester, when all that's needed is an increase of just 200 calories a day. This is the equivalent of a couple of slices of toast with low-fat spread and a glass of milk.

There is no need to increase your protein intake, as long as you follow general healthy eating principles and include some lean meat, fish or poultry, dairy products, grains, nuts and pulses.

It's particularly important to increase your fibre intakes when pregnant to avoid the common pregnancy niggles of constipation and piles (haemorrhoids). Increase your fibre intake by eating lots of fruit and vegetables, wholemeal bread and cereals, brown rice, wholemeal pasta and pulses. You should also increase your fluid intake. Increasing fibre without adequate fluid can exacerbate constipation.

This is particularly important before conception and during the first trimester of pregnancy. Mothers who are deficient in folic acid are at increased risk of having a baby with a neural tube defect (NTD), such as spina bifida.

From the moment you start trying to conceive until week 12 of pregnancy, you should take a daily 400mcg supplement of folic acid. Women with a history of NTDs should be prescribed a 5mg supplement.

These supplements should be in addition to dietary intakes, which should be about 200mcg per day. You can boost your folic acid intake by choosing foods such as:

Folic acid is easily lost during cooking, so steam vegetables or cook in only a little water for a short time to retain as much goodness as possible.

Many women of child-bearing age have low iron stores. Your iron levels will be measured throughout pregnancy, and if found to be low you'll be prescribed an iron supplement. Nevertheless, it's important to try to maintain a good iron intake during pregnancy.

Good sources of iron can be split into two categories: meat-based (haem) and plant-based (non-haem):

The body doesn't absorb iron from non-meat foods as easily as it does from meat sources. However, you can enhance iron absorption by including a source of vitamin C (see below) with your meal. In contrast, tannins found in tea reduce the absorption. So, it's better to have a glass of orange juice with your bowl of cereal in the morning than a cup of tea.

Although liver and liver products, such as paté and liver sausage, are good sources of iron, they can also contain very high concentrations of vitamin A. If taken in excess, this vitamin can build up in the liver and cause serious harm to a growing baby.

As a result, the Department of Health advises all pregnant women to avoid liver and liver products. You should also be aware that some vitamin supplements are high in this vitamin, so always choose a specially prepared pregnancy supplement.

However, the form of vitamin A derived from green, orange, and yellow fruit and vegetables - known as carotene - has very positive health benefits, and is plentiful in red, yellow and orange peppers, mango, carrots, sweet potatoes, apricots, tomatoes and watercress.

In order to help your body absorb and effectively use iron and other nutrients from your food, you should eat plenty of vitamin C-rich foods. Good sources include citrus fruits (oranges, tangerines, grapefruit and lemons), blackcurrants, strawberries, kiwi fruit, peppers, tomatoes and green leafy vegetables. Aim to eat at least five portions of fruit and vegetables every day.

This is sometimes referred to as the 'sunshine vitamin' because it's made when the skin is exposed to sunlight. Vitamin D is essential for the proper use of calcium and phosphorus, which are necessary for the formation and maintenance of healthy bones and teeth. It is found in only a few foods, including fortified margarines and reduced-fat spreads, fortified breakfast cereals, oily fish and meat. A small amount can also be found in milk and eggs.

Pregnant and breastfeeding women with dark skin or those who always cover their skin, are at particular risk of a vitamin D deficiency and may require a supplement. These should be available at your local health centre. Ask your dietician, practice nurse or doctor for more information.

Your requirements of this essential mineral double during pregnancy, and are particularly high during the last ten weeks when calcium is being laid down in your baby's bones. Despite this, though, no dietary increase is thought necessary because your body adapts to absorb more calcium from the foods eaten.

This means, though, that it's important to eat sufficient calcium-containing foods. Good sources include milk and dairy foods such as cheese, yoghurt and fromage frais. Pregnant women should aim to have three servings of foods from this group every day (typical servings include a glass of milk, milk with cereal, a small chunk of cheese and a small pot of yoghurt). Other sources include bread, green vegetables, canned fish with soft, edible bones (salmon, sardines and pilchards), dried apricots, sesame seeds, tofu, fortified orange juice and fortified soya milk.

If you're pregnant or breastfeeding and you receive Income Support of Jobseeker's Allowance, you're entitled to free milk (up to seven pints a week). Ask your midwife or health visitor for further details.

Most of the additional nutrient needs of pregnancy can be met by eating a well-balanced and varied diet. With a few exceptions, you can continue to eat a normal, healthy diet in keeping with the Balance of Good Health. This includes regular meals and snacks, and a sensible healthy eating regime containing: