Macronutrients are nutrients such as protein and carbohydrates?which are converted into energy, to be used by the body to fulfil essential functions and perform physical tasks. They are obtained from a variety of food sources including cereals and grains, meat and legumes. During pregnancy macronutrients provide the energy necessary for foetal growth and maintenance of the woman’s weight and essential bodily functions (e.g. respiration). Macronutrient requirements therefore increase during pregnancy because the growing baby requires energy as well as the woman’s body. Ensuring energy intake increases accordingly is essential for optimal health outcomes for both the pregnant woman and her baby.
An individual who does not consume enough energy becomes malnourished, and malnutrition?has a range of health consequences for a pregnant woman and her growing baby. These include a greater risk of low-birth weight?and infant mortality. Low birth rate is the most important factor which causes illness and death in babies. It is also associated with a variety of infant and childhood development disorders, in particular poor cognitive (mental) development. Low birth weight also increases an individual’s risk of developing chronic health conditions such as diabetes later in life.
During pregnancy, a woman’s energy requirement increases because she expends more energy. That energy is used to:
Basal energy expenditure
A woman’s BEE increases progressively throughout the course of the pregnancy. In the first trimester she will expend, on average, an additional 4% of her pre-pregnancy BEE. In the second?and third trimesters?she will expend an additional 7% and 19% of her pre-pregnancy BEE respectively. Thus depending on the stage of pregnancy, a woman will have different energy requirements. In the first trimester of pregnancy women have no additional macronutrient requirement. In the second trimester it is recommended that women consume an additional 240 calories of energy per day, which increases to 452 calories per day in the third trimester.
Physical activity
In addition to an increased BEE, the amount of energy expended performing equivalent physical activities is higher in the third trimester of pregnancy compared to pre-pregnancy. For example, one study showed that walking on a treadmill expended 19% more energy after 25 weeks gestation, than pre-pregnancy.
A woman’s level of physical activity during pregnancy plays an important role in determining her total energy requirement and physically active women must consume more energy than inactive women to ensure they meet their energy requirements. For example, pregnant women who are:
Resting - chair or bed bound should consume approximately 1,900 calories per day;Exclusively sedentary - spend most of the day sitting and do little walking or other physical activity should consume 2,175-2,300 calories per day;Sedentary with some activity - spend most of the day seated but also do light physical activity such as walking should consume 2,435-2,570 calories per day;Active - spend large parts of the day standing or walking should consume 2,700-2,850 calories per day;Highly active - work as labourers or perform considerable strenuous exercise such as running should consume 2,990-3,250 calories per day.
Growth
During pregnancy the woman grows many new tissues which form the products of birth, the foetus and maternal tissue (e.g. enlarged breasts). Collectively these tissues will weigh an average of 12.5kg (in a typical woman who bears an infant weighing 3.4kg) and the fats and proteins which are deposited to form these tissues come from the energy the pregnant woman obtains from food.
As a woman’s energy expenditure increases during pregnancy, her macro-nutritional requirements also increase and she must consume more food.
During the first trimester of pregnancy there is generally no need for women to increase the amount they eat, although increasing food intake is recommended for women with a Body Mass Index (BMI) <20.
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In the second and third trimesters of pregnancy, women need to consume additional food to account for the energy requirements of pregnancy. Pregnant women should aim to increase their energy intake by 240 calories per day in the second trimester and 452 calories per day in the third trimester of pregnancy to account for their additional energy requirements.
Women should try to consume additional healthy foods (not snacks or confectionary) from a variety of food groups to meet their additional calorie requirement and also provide important micronutrients to their body and foetus. The additional calories should include an extra serving of cereal, but also protein and micronutrient rich foods, particularly fruit and legumes.
Healthy foods which women might consume to meet their additional calorie requirement of 240 calories in the second trimester of pregnancy include:
Couscous (100g) with mixed stir-fried vegetables (200g) - 232 calories;Ham sandwich (wholemeal bread with 50g ham) and an orange (200g) - 271 calories;2 slices of bread with peanut butter - 276 calories;White rice (100g) with grilled lean beef (80g) and mixed stir-fried vegetables (100g) - 274 calories;Berry smoothie made with low fat milk and ice cream (300ml) - 218 calories;Reduced fat fruit yoghurt (200ml) and fresh strawberries (200g) - 226 calories;Cottage cheese (40g) sandwich with whole grain bread - 190 calories; orGlass of skim milk and a serve (30g) of peanuts - 240 calories.
Healthy foods which women might consume to meet their additional calorie requirement of 452 calories in the third trimester of pregnancy include:
Food
A healthy diet during pregnancy, like a healthy diet at other times, consists of various quantities of foods from different food groups. Women who are vegan or vegetarian may find it more difficult to consume foods from all food groups and should consult a dietician for nutritional advice.
Cereals, including bread, pasta, rice and noodles
It is recommended that pregnant women consume 4-6 servings of cereals each day. Examples of foods which are equivalent to a single serve of cereal include:
Vegetables and legumes
Pregnant women should consume 5-6 serves of vegetables or legumes everyday. These serves should include vegetables which are leaves, roots, stems and seeds of plants as well as fruits such as tomatoes and pumpkin which are used like vegetables (e.g. in cooking and salad). Pregnant women should eat a variety of vegetables each day, including dark and light leafy vegetables, orange and starchy vegetables and legumes. Examples of foods which are equivalent to a single serving of vegetables include:
1/2?cup of cooked vegetables;1/2?cup of cooked beans or legumes;1 cup of raw salad vegetables; or1 small potato.
Fruit
Pregnant women need to eat more fruit than non-pregnant women and it is recommended that they consume 4 serves of fruit each day. Fresh, canned, juiced or dried fruit can all be consumed, although the majority of serves should be fresh fruit. A variety of types of fruit should be eaten, for example melons, stone fruit, citrus and tropical fruit. Examples of fruits which are equivalent to a single serve include:
1 medium piece of fruit, for example an apple, banana or pear;2 small pieces of fruit, for example kiwi fruits, apricots or plums;1 cup of fresh diced fruit (e.g. pineapple) or canned fruit;1/2?cup of fruit juice; orEquivalent quantities of dried fruit (e.g. 4 dried apricot halves equal 2 small apricots).
Dairy products
It is recommended that pregnant women consume 2 serves of dairy products each day to fulfil their nutritional requirements. Pregnant women who are concerned about consuming too much fat should eat reduced fat dairy products, which have all the nutrients of full fat products, without most of the fat. Examples of foods which are equivalent to a single serving of dairy include:
Individuals who do not consume dairy products because of intolerance or personal choice may alternatively consume:
Meat or other protein containing foods
Pregnant women should continue to consume?1 serve of meat or other protein containing foods each day. Meat and protein containing foods which are equivalent to a single serve include:
65-100g of cooked lean meat or chicken (fatty meat should be avoided to reduce the total fat content of the diet);80-120g of cooked fish fillet;2 small eggs;1 cup of cooked legumes;1/3 cup of nuts; or1 cup of sesame seeds.
Fats and sugars should be eaten only in small quantities during pregnancy.
Water
It is also important for pregnant women to drink plenty of water, as water is an essential nutrient and demand for water increases during pregnancy. It is recommended that women drink at least 8 glasses of water each day during pregnancy.?
A pregnant woman’s macronutrient requirement refers to the total amount of energy (measured in calories) which she must consume to maintain her body weight, perform physical activity, account for gestational weight gain and maintain essential bodily functions. It increases throughout the pregnancy and women must therefore consume more calories in their daily diet whilst they are pregnant. The recommended quantities of food for a pregnant woman to eat on a daily basis (outlined above) are therefore higher for pregnant than non-pregnant women, for example it is recommended that pregnant women eat additional servings of fruit and vegetables, which provide both macro and micronutrients.
Maintaining adequate energy intake during pregnancy is important to ensure that the body has sufficient energy for maintenance, pregnancy related growth and physical activity. As a woman gains weight during pregnancy, her energy requirements increase with increasing weight gain.
Normal weight women (women with a BMI 18.5-25) who consume a healthy balanced diet should expect to gain 1.6kg in the first trimester of pregnancy and 0.44kg per week thereafter. Overall, an average weight gain of 12.5 kg is expected for a normal weight woman (BMI 22.5kg/m2) who bears an infant weighing 3.4kg. However, gestational weight gain varies from woman to woman depending on pre-pregnancy BMI. Women who are already overweight before pregnancy typically gain less weight, while those who are underweight prior to conception will gain weight at a faster rate.? Women bearing multiple pregnancies may have greater weight gain.
Weight gain is an important indicator of good nutrition and foetal development during pregnancy. Extra blood volume, enlargement of the breasts and growth of the placenta and uterus will necessarily increase weight. Maternal weight gain of less than 10kg by 40 weeks of gestation is a risk factor for intrauterine growth restriction (IUGR).
For fear of delivering large babies, some women purposely restrict their food intake whilst pregnant. This may be particularly true for women who have immigrated to Australia from countries where cultural beliefs about eating are very different. However, there are no benefits to a woman or her growing baby’s health associated with restricting food intake in pregnancy. On the contrary, not eating enough is associated with numerous health risks. Women should therefore avoid restricting their food intake, due to the numerous health risks it entails.
?For more information about pregnancy, including preconception advice, stages of pregnancy, investigations, complications, living with pregnancy and birth, see?Pregnancy.
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