Nutrition - Diet in pregnancy: Quality not quantity

As well as following general healthy eating advice, Fiona Dunlevy outlines additional considerations for pregnant women

Healthy eating has advantages for health throughout life. It is particularly important to eat healthy food prior to conception and throughout pregnancy but all women of child-bearing age should watch their diet, as up to 50% of pregnancies are unplanned.

Preconception diet
All women of child-bearing age should take a folic acid supplement of 400µg a day or if there is a family history of neural tube defects they should take 5mg a day.

While many foods available throughout Europe are fortified with folic acid normal intake would not suffice to prevent NTDs without a supplement.

It is important to follow healthy eating guidelines. When planning a pregnancy, women should steer clear of any fad diets. Overweight or obese women should avoid fat and sugar in their diet.

Supplements containing vitamin A should be avoided, including fish liver oil. A high dose of vitamin A in early pregnancy can have teratogenic effects. Women should avoid alcohol throughout pregnancy particularly in the early stages. Alcohol should be limited to one to two units a week, however even this amount may be harmful.

Women with type 1 and type 2 diabetes can significantly reduce risks of complications by achieving good blood sugar control in early pregnancy. They should be advised to follow a strict glucose-controlled diet and to consult with their endocrINOlogist, diabetes nurse and dietitian when planning a pregnancy.

Women with PKU should ensure their diet is free from phenylalanine and should be referred to a specialist dietitian for dietary manipulation. Women with coeliac disease may be at risk of low iron or calcium, and supplements should be given if necessary.

Diet in pregnancy
During pregnancy it’s the quality of food rather than the quantity that is most important. The food pyramid provides a good base for planning a healthy diet.

The average weight gain in pregnancy is 7-12kg but can be more in underweight women or those with multiple pregnancies. In the third trimester an additional 200-300kcal is required to meet energy demands due to the increase in basal metabolism. Patients should be resting towards this stage.

A further increase in intake may be required for women who continue to work. A woman’s appetite is the best guide as she should not be hungry. Patients with a family history of diabetes or who are overweight or obese before pregnancy should be advised to restrict sugar and fat in their diet. Confectionery foods such as sweets and crisps are not essential and can lead to excess weight gain so should be limited by all pregnant women.

Protein is important for the growth and development of new tissue. Most varied diets will be adequate in protein but vegetarians should be advised to include extra foods high in protein. Foods containing protein include meat, poultry, fish, eggs, beans, lentils, dairy products and tofu.

Iron is in high demand in pregnancy for foetal growth, placenta and the expanded maternal red-cell mass. The body adapts to assist maintenance of adequate iron stores – menstruation ceases and the iron absorption in the gut increases progressively during pregnancy. Therefore routine supplementation with iron is unnecessary. However, iron supplementation is required in those with poor intake of iron prior to pregnancy, in all women who smoke and also in those from lower socio-economic backgrounds.

Spa water (a natural water from iron-rich soils) is useful to maintain iron levels in the healthy pregnant population but would not be sufficient for those with low levels of iron. A high dose iron supplement is required for those with low iron.

A good dietary intake of iron is essential in all women – the best source is red meat, which should be consumed three times a week. Other good sources include green leafy vegetables, beans, lentils and fortified cereals. Vitamin C is needed with these foods to maximise absorption. Foods containing tannins, such as tea, should be avoided with meals as they block absorption of iron.

Calcium is essential for formation of healthy bones and teeth in the baby, and the prevention of bone loss in the mother. The body adapts by enhancing bone turnover, intestinal absorption and decreasing urine excretion. However, this is not always enough to meet demands and it is very important to increase sources of calcium during pregnancy, particularly after week 30.

Women are recommended to choose five portions from the dairy group on the food pyramid as opposed to the usual three. For patients who avoid dairy products a supplement may be required; ideally the supplement should be prescribed with dose being dependent on dietary intake. Supplements used include Calcichew, Calcichew D3 and Calcium-Sandoz.

Vitamin D
Vitamin D is essential for the absorption of calcium. Infants born to women with low vitamin D status have increased incidences of hyperparathyroidism and neonatal hypocalcaemia. Good sources include fortified milk, margarine, oily fish, cereals, eggs and meat.

Vitamin D is also synthesised by sunlight; there is evidence to suggest all women should be supplemented with vitamin D in winter months, especially women with darker complexions. Women who cover up their skin should take a vitamin D supplement throughout pregnancy. Calcichew D3 can be used in such cases. These women should continue taking vitamin D while breastfeeding.

Nausea during early pregnancy is common and usually the body contains enough stores to nourish the baby. However, continued vomiting episodes can compromise nutritional status. Women should be encouraged to eat small meals frequently and avoid long gaps between eating. Foods high in fat, spice and citrus fruits should be avoided. Fluids should be encouraged to prevent dehydration. Patients with persistent vomiting may require admission for IV rehydration. Fluids should be sipped slowly through a straw and fizzy drinks served flat. Food should be fluid-based, such as jelly and soup, to maximise intake.

Heartburn is common in the third trimester and many antacids are suitable in pregnancy. However, women with diabetes should be careful of the sugar content of antacids. Patients should be advised to avoid spicy, fatty foods and fizzy drinks. They should eat slowly and avoid eating late at night.

This can occur at any stage but is common in late pregnancy. It is mainly due to changes in gut function, reduced activity and lack of fluids. Women taking iron supplements will be prone to constipation. Fluid intake should be increased progressively throughout pregnancy and by the third trimester, women should be taking at least an extra 500ml a day.

They should increase their intake of fibre with foods such at fruit, vegetables and high fibre cereals; additional fluid is needed when taking a high fibre diet. If this is not enough they can be encouraged to try linseed, prunes or prune juice. Some women may require a laxative.

Teenagers who become pregnant are at risk of malnutrition in pregnancy as they are still growing. They may try to conceal the pregnancy by not eating. Therefore these patients need care and particular attention to ensure they meet their nutritional requirements.

Foods to avoid

Toxicological hazards
Alcohol: Alcohol is not an essential nutrient and can interfere with the absorption of zinc, folate, magnesium and iron. Patients should be advised to avoid alcohol during pregnancy.

Vitamin A: This vitamin is essential in the diet, however, excess amounts in pregnancy are known to be teratogenic and can lead to congenital malformations of the brain, eyes and skeleton. All supplements containing vitamin A need to be avoided during pregnancy, including multivitamins and cod liver oil. Foods with a high vitamin A content, eg. liver and pate should also be avoided.

Fish: Farmed fish, including many oily fish, contain dioxins and should be limited to twice a week. Tuna and fish at the top of the food chain including shark, marlin and swordfish contain mercury and should be limited to twice a week. However, oily fish does contain omega-3 which has many reported benefits so these foods should not be eliminated completely.

Many fish oil supplements contain dioxins at various levels so these should be avoided. If a patient dislikes oily fish they can increase their omega-3 consumption by including linseeds.

Caffeine: Large doses may be teratogenic and may increase risk of complications in pregnancy. Women should be advised to limit caffeine drinks, for example, to two cups of coffee a day.

Herbal teas: The evidence is inconclusive on many herbal teas so it’s best to recommend avoiding herbal teas.

Food borne diseases
Due to the potential adverse effects of food borne diseases in pregnancy, foods likely to contain them should be avoided. These foods do not need to be avoided when breastfeeding. They include potential sources of listeria, toxoplasmosis and salmonella.

Food hygiene is essential during this time and women should be advised on hygienic food storage, preparation and hand hygiene. Any raw or cured meat should be avoided; instead meat should be cooked thoroughly.

Food should only be reheated once and must be piping hot throughout after reheating. Eggs must be cooked until hard throughout and women should be advised to avoid potential under-cooked egg, in fried rice for example.

Soft and ripened cheeses have a higher pH resulting in an increased risk of listeria growth so they should be avoided. It is important to check the best-before date on foods before eating them. Soft whipped ice cream and soft foods at deli counters should also be avoided.

Although the evidence is still under investigation, women with a family history or whose partner has a family history of atopic diseases should avoid excess nuts during pregnancy, although traces of nuts do not need to be avoided. If the mother is avoiding any foods due to intolerances or allergies she may benefit from a dietetic consultation to ensure that her diet is adequate.

Fiona Dunlevy is a clinical nutritionist at the Coombe Women’s Hospital, Dublin

References on request from nursing at by quoting: Dunlevy F. WIN 2006; 14(4): 43-44
MedMedia note – email author if there are any requests for refs)

 Nutrition - Diet in pregnancy: Quality not quantity


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