Contrary to popular belief you don’t need to ‘eat for two’ when you’re pregnant. Your body becomes more efficient at using the energy and nutrients from your diet, so simply eating healthily is the key. Your body does however have extra calorie requirements in later pregnancy and increased needs for certain other nutrients. This article explores your nutritional requirements during pregnancy, and provides information and tips to help you to meet these.

What is ‘RNI’?

RNI stands for ‘Reference Nutrient Intake’. It’s the amount of a nutrient that meets the needs of 97.5% of the UK population. RNI figures are based on the population, not individual requirements. Although often similar, RNIs shouldn’t be confused with RDAs (‘Recommended Dietary Allowances’). RDAs were developed by the US Food and Nutrition Board, so don’t originate from the UK. Unfortunately there is no UK standard system; supplements seem to use RDA more frequently than RNI, making it difficult for consumers to understand labels.

First off, let’s have a look at the RNIs in pregnancy. We will then discuss these individually, along with other nutrients which are still important, but which we are not recommended specifically to increase during pregnancy. The table below compares daily RNI for non-pregnant women with the requirements in pregnancy:

Nutrient Non-pregnant daily RNI Increase in pregnancy
Energy (kcal) Around 2000kcal (depending on weight and activity levels) Extra 200kcal in the 3rd trimester only
Folic acid (mcg) 200 Extra 400 (1st trimester)
Extra 100 (2nd and 3rd trimesters)
Protein (g) 51 Extra 6g
Vitamin C (mg) 40 Extra 10mg (3rd trimester only)
Vitamin D (mcg) 0 (assumed gained from sunlight action on skin, although the RNI is 10 if you are in an ‘at risk’ group) 10mcg
Vitamin A (mcg) 600 Extra 100 mcg
Table adapted from Webster-Gandy et al (2011), Oxford Handbook of Nutrition and Dietetics 2nd Edition, Oxford University Press.


There is no increased calorie requirement until the third trimester. During pregnancy, your body becomes very efficient at absorbing the nutrients it needs, and altering metabolism, so you can gain weight without increasing your food intake. It’s important to try not to over-eat in pregnancy, so that you don’t put on too much weight. In the third trimester, be guided by hunger, but to make sure you choose healthy snacks, and avoid snacking on foods high in sugar or fat. Examples of healthy snacks containing 200 kcal are as follows:

  • 2 rice cakes with low fat hummus and a piece of fruit
  • 2 portions of fruit, some carrot & cucumber sticks and low fat hummus dip
  • Sandwich with low fat cream cheese
  • 1 slice of cheese on toast
  • 25g (1oz) nuts and a piece of fruit

Folic acid

An extra 400 micrograms is required in the first 12 weeks of pregnancy, which should be taken as a supplement. This is to help prevent neural tube defects in the developing baby’s tender nervous system. You don’t need to continue supplements after the first 12 weeks if you’d rather not, but many women choose to take a pregnancy multi-vitamin tablet or Healthy Start vitamins, which contain 400 micrograms of folic acid. Good sources of folate to include during pregnancy include fortified breakfast cereals, green leafy vegetables, bread and brown rice.


There is an additional requirement of 6g of protein during pregnancy. Protein is needed for the growth and development of the baby’s body and muscles. Protein requirements should easily be met with a normal healthy diet. Try to eat 2-3 protein-rich sources a day, such as meat, fish, eggs, cheese, tofu, Quorn, beans and pulses. Choose low fat and lean varieties wherever possible.

Vitamin D

The Department of Health recommends that all pregnant women take a daily supplement containing 10 micrograms of vitamin D. This is to support your developing baby’s bones and help prevent rickets in your baby. This supplement should be in addition to vitamin D made by the action of sunlight on skin, and in addition to dietary sources of vitamin D.

Vitamin C

Vitamin C is needed for both you and your baby to make collagen, a protein found in bones, cartilage, skin and bones. It also helps us make healthy cells and fight infections. There is an extra 10mg requirement in the last trimester of pregnancy. This should not be difficult to achieve by eating five portions of fruit and vegetables each day. Good sources of vitamin C include:

  • Fruit, especially citrus fruits (e.g. oranges, grapefruit) and berries
  • Fruit juice, especially orange, apple, pineapple, tomato and cranberry
  • Potatoes
  • Vegetables, e.g. peas, tomatoes, peppers, broccoli, cabbages, courgettes and spinach

Vitamin C is lost from foods by over-cooking. To preserve their vitamin content, boil vegetables quickly in minimal water, or steam them.

Vitamin A

Although the requirements are slightly higher in pregnancy, be sure to avoid liver and liver-containing products because they are too high in vitamin A. One portion (100g) of liver may contain 18 times the RNI for vitamin A, and such levels may be toxic to your growing baby.

Studies show that around 15% of women of child-bearing age do not eat enough vitamin A. Vitamin A is obtained in safe amounts by including dairy products, oily fish, fruits and vegetables in the diet. Oily fish, e.g. salmon, sardines, pilchards and mackerel should be encouraged once a week in pregnancy, not only for its omega-3 oil content, but also its vitamin A content. Avoid any supplements containing vitamin A and don’t take cod liver oil during pregnancy.


During pregnancy the body increases the amount of calcium it absorbs, so the baby is still able to get enough calcium without you increasing your intake. The RNI for calcium is 700mg (800mg for pregnant teenagers). Studies show that 5-19% of women of child-bearing age do not eat enough calcium. To get enough calcium, try to eat 2-3 dairy products a day, e.g. milk with cereal, yoghurt and some cheese. A glass of milk, matchbox size of cheese or pot of yoghurt each contain around 200-250mg of calcium. If you avoid dairy foods, e.g. are vegan or lactose intolerant, you can get calcium from calcium-enriched soya/rice milk, soya yoghurts, calcium-enriched tofu, kidney/soya beans, tempeh, soya mince, nuts, figs and green leafy vegetables.


The RNI for iron is 15mg, the same as for non-pregnant women. There’s no evidence to recommend increasing iron intake for pregnant women. Iron is an important nutrient to consider though because pregnant women tend to be susceptible to iron deficiency anaemia. Studies show that 25-50% of women of child-bearing age do not eat enough iron. Iron supplements are only advised if there’s evidence of anaemia.

Top 5 dietary sources of iron for pregnancy:

Food and portion Amount of iron
Lentils (4 tablespoons, cooked) 4½mg
Breakfast cereals, fortified – e.g. ready brek, All Bran, cornflakes, Weatabix (30g) 3mg
Beef (100g) 3mg
Baked / kidney / butter / soya beans & chickpeas (4 tablespoons) 3mg
Tinned pilchards / sardines (1 small tin / 100g) 2½mg

Vitamin C helps the body to absorb iron from food, so try to include a source of vitamin C at each meal.


    Great Britain: Committee on Medical Aspects of Food Policy and Great Britain: Department of Health (1991) Dietary reference values for food energy and nutrients for the United Kingdom. Stationery Office Books.

    Henderson et al (2003) The National Diet and Nutrition Survey: adults aged 19-64 years. HMSO Crown Copyright (Accessed August 2013).

    McCance RA and Widdowson EM (2002). McCance and Widdowson's The Composition of Foods Sixth Summary Edition. Royal Society of Chemistry.

    Webster-Gandy J et al (2011). Oxford Handbook of Nutrition and Dietetics, 2nd Edition. Oxford University Press.