Nutrient needs increase during pregnancy and good nutritional health is important to help ensure optimal health for the mother and to provide an optimal start to life for the baby. Maintaining a healthy diet during pregnancy is not complicated and can largely be achieved through appropriate food choices.
Women require additional energy in the second and third trimester to support the growth demands of the baby. The additional energy needed however is quite small and most women can easily meet this from only modest increases in food intake. Within Australia and New Zealand there are two public health documents that provide the foundation for evidence based food and nutrient recommendations for healthy populations. These documents are the Nutrient Reference Values (NRV)(1) and the Australian Dietary Guidelines(2).
The NRV recommend an additional 1,400kJ (335 kcal) per day in the second trimester and an additional 1,900kJ (455kcal) per day in the third trimester. A woman who enters pregnancy overweight or obese will need to consume less than this and an underweight women would need an additional 150 kJ per day more. The Australian Dietary Guidelines have translated this additional need into recommended food patterns and recommend that this additional energy comes from 2½ additional servings of grain (cereal) foods and 1 additional serving from the lean meats and alternative food group.
Measuring weight gain during pregnancy is a simple and effective way to determine if energy intake is meeting the needs for appropriate growth.
The amount of weight gained during pregnancy is important for the short term and long term health of both the mother and the baby. Ideally, between 1-2kg of weight is gained during the first trimester and approximately 0.5kg per week for the remaining two trimesters. The US Institute of Medicine recommends the following weight gain during pregnancy (Table 1)(3).
Recommendations for weight gain during pregnancy
|Pre-pregnancy BMI||Recommended weight gain|
|Less than 18.5 kg/m2||12.5 to 18kg|
|18.5 to 24.9 kg/m2||11.5 to 16kg|
|25 to 29.9 kg/m2||7 to 11.5kg|
|Above 30 kg/m2||5 to 9kg|
[Adapted from the IOM (3)]
Excess weight gain is associated with increased risk of maternal hypertension, gestational diabetes, postpartum haemorrhage, caesarean section and a large for gestational age (LGA) infant who weighs more than 4000gm. Insufficient weight gain has been shown to result in an increased risk of delivering small for gestational age infants(4).
Ideally, a woman who is planning a pregnancy should work towards achieving a healthy body weight as measured by Body Mass Index (BMI weight in kg/height in meters2) before becoming pregnant. Women entering pregnancy overweight or obese increase their risk of adverse health outcomes such as gestational diabetes, hypertension, caesarean delivery and increased hospital stay(5). Weight reduction for overweight or obese women is not recommended during pregnancy, but the amount of weight gain should be smaller than those who enter at a normal BMI(3). Underweight women, as assessed by a BMI below 18.5kg/m2 are recommended to gain more weight to help ensure a healthy birth weight for the infant.
Protein needs increase during the 2nd and 3rd trimesters of pregnancy but this increased need is easily meet by current dietary patterns. Protein supplements are not recommended during pregnancy.
Recommended dietary intake of protein during pregnancy
|Age group||Woman 19-50 years||Pregnant women 19-50 years||Food sources|
|Protein||0.75gm/kg body weight||1.00gm/kg body weight||Wide spread in most foods. Recommended increased serves of grain (cereal foods) and lean meats and alternatives|
*Nutrient Reference Values(1)
Essential fatty acids are required by the developing foetus for optimal growth, especially for the development of the brain, nervous system and eyes. Good sources of essential fatty acids include oily fish (e.g. salmon, tuna and mackerel), eggs, lean meat, nuts and seeds and their associated oils. The NRVs recommend an Adequate Intake (AI) of long chain essential fatty acids of 90mg/day for an adult woman (85mg/day for a teenage woman 14-18 years) and this increases to 115mg/day during pregnancy (110mg/day for a teenage woman) to account for the extra needs of the developing foetus. These recommendations have been established based on median population intakes within Australia.
Due to the changes within the gastrointestinal tract and water reabsorption in the kidneys, pregnant women can experience increased difficulty passing a bowel motion and constipation. As a result, increased fibre intake is recommended during pregnancy. For adult women, the recommended increase is from 25gm/day to 28gm/day during pregnancy, and for women aged 14-18years, the increase should be from 22gm/day to 25gm/day. Vegetables, wholegrains, beans, legumes and fruit are good sources of dietary fibre and following a dietary pattern recommended in the Australian Dietary Guidelines will help pregnant women meet this increased need.
Water soluble vitamin needs generally increase during pregnancy, but for the fat soluble vitamins, only Vitamin A needs increase. Most of these increased requirements can be met by the increased food intakes recommended during pregnancy, with the exception of folate.
Folate is a B vitamin required for the production of red blood cells, cell division and for the healthy development of the neural tube. The RDI for pregnant women is 600µg/day, which may be challenging for women to meet without the use of fortified foods. In addition, it has been recognised for nearly two decades that increased folate in the form of folic acid during pregnancy can significantly decrease the risk of having a pregnancy affected by a neural tube defect (NTD).
Therefore, the NHMRC recommend further that for both pregnant women and for those planning a pregnancy that an additional 500µg/day of folic acid be consumed in the form of a supplement(7). A woman with an increased risk of having a baby with a NTD (i.e. a woman who has had a baby with a NTD previously or whom has a close relative with a baby with a NTD) is recommended to consume 5mg/day of folic acid.
Recommended Dietary Intake of vitamins during pregnancy
|Age group||Women 19-50 years||Pregnant women 19-50 years||Food sources|
|Vitamin B6||1.3mg/day||1.9mg/day||Meat, fish, poultry, wholegrains|
|Vitamin B12||2.4μg/day||2.6μg/day||Meat, seafood, poultry and dairy products|
|Folate||400μg/day||600μg/day||Vegetables, legumes, fruit, wholegrains, fortified foods|
|Vitamin C||45mg/day||60mg/day||Fruit, vegetables|
|Vitamin A||700μg/day||800μg/day||Red, yellow vegetables, dairy products, vegetable oils|
|Vitamin D||5μg/day||5μg/day||Small amounts in limited foods. Produced in the body following sunlight.|
*Nutrient Reference Values(1)
The need for some, but not all, minerals increases during pregnancy. The increased recommendation for iodine is difficult to meet from food alone and dietary intakes plus supplementation is recommended.
The NRV recommends that pregnant women consume 27mg/day iron during pregnancy. This level of iron intake is challenging to achieve through dietary intake. The sample meal plan below provides an indication of how to achieve close to the recommended dietary iron intake. Monitoring iron status during pregnancy is important help to identify women at risk of low iron who may benefit from iron supplementation.
|Iron fortified breakfast cereal with milk Two kiwifruit or a glass of vitamin C rich juice Two slices wholegrain toast with spread (ideally a nut based spread)|
|Dried fruit and nuts (almonds are a good choice)|
|Wholegrain bread sandwich with a lean meat filling Large vegetable salad including legumes such as lentils or chickpeas Yoghurt|
|Glass milk with Milo (iron fortified) Wholemeal crackers with humus|
|Lean red meat, wholegrain, cereal and plenty of vegetables Fruit for desert|
There is no recommendation to consume additional calcium during pregnancy. This is because there is a significant increase in a woman’s ability to absorb and retain calcium during pregnancy. These adaptations work to provide sufficient calcium necessary for foetal growth without an increase in maternal dietary intake and without compromising long term maternal bone health. Dietary calcium intake does not appear to influence changes in maternal bone mass in pregnancy and there is no relationship between the number of previous pregnancies and bone mineral density or fracture risk.
It appears that current intakes of zinc are close to the recommended levels needed during pregnancy. The Australian Dietary Guidelines recommendation to consume more grain (cereal) products and lean meat and alternatives during pregnancy will help to meet the increased zinc needs, because these foods are good sources of zinc.
Iodine requirements increase to 220µg/day during pregnancy, due to the increased production of thyroid hormones. The foetus requires iodine for normal brain and nervous system development. Mild to moderate iodine deficiency can cause learning difficulties and affect physical development and Australia is recognised by the WHO as mildly iodine deficient(8).
Iodine can be found in foods such as fortified bread products, shellfish, iodised salt, eggs and sea vegetables. In 2009, Australia and New Zealand introduced mandatory fortification of salt used in bread making in order to improve the iodine status of the population(9). Since the introduction of this fortification program, iodine levels in pregnant women in Australia appear to have increased. A study looking at a small sample of pregnant women in NSW observed that urinary iodine levels have increased from a median of 88µg/L in 2008 (pre-fortification) to 145 and 166µg/L in 2011 and 2012 respectively. They observed further that women who were taking iodine supplements had significantly higher iodine levels than women not taking supplements (178 and 202µg/L compared with 109 and 124µg/L 2011 and 2012 respectively)(10). Therefore, it appears that the NHMRC recommendation that all women who are pregnant, breastfeeding or considering pregnancy take an iodine supplement of 150µg/day remains valid(11) and these supplements are required to ensure adequate iodine status in pregnant women.
|Age group||Women 19-50 years||Pregnant women 19-50 years||Food sources|
|Calcium||1000mg/day||1000mg/day||Milk, dairy products and calcium fortified alternatives such as soy milk|
|Iodine||150μg/day||220μg/day||Milk, dairy products, fortified bread, shellfish, iodised salt|
|Iron||18mg/day||27mg/day||Vegetables, legumes, fruit, wholegrains, fortified foods|
|Zinc||8mg/day||11mg/day||Milk, meat, wholegrain, legumes|
*Nutrient Reference Values(1)
The NRV recommend that people over the age of 14 years consume no more than 600mg/day of sodium, in order to reduce the risk of dietary related chronic diseases such as high blood pressure. This recommendation is also appropriate for pregnant women. Within Australia, most of the population is consuming well in excess of this recommendation.
The majority of our sodium comes from the salt provided in processed foods. Therefore, pregnant women should be advised to select foods low in salt (ideally less than 120mg per 100gm food but no more than 500mg per 100gm food) wherever possible and avoid adding salt either at the table or during cooking. To reduce the risk of high blood pressure, the NRV further recommend consuming 320mg/day of potassium, these recommendations also apply to pregnant women. Increasing intakes of fruits, wholegrains, vegetables and dairy products will improve potassium intakes.
The Australian Dietary Guidelines provide recommendations for the types and amounts of foods to consume during pregnancy. These recommendations are designed to help a woman achieve the nutrient recommendations described above with the exception of iron. Following an eating pattern consistent with the recommendations below will help pregnant women to meet their nutrient needs.
Recommended number of serves of food groups for women during pregnancy
|Vegetables and legumes||Fruit||Grain (cereal) foods, mostly wholegrain||Lean meats, poultry, fish, eggs, tofu, nuts and seeds, legumes||Milk, yoghurt, cheese and/or alternatives||Extra foods|
Australian Dietary Guidelines(2)
An adequate intake of dietary iron can help to prevent the development of iron deficiency anaemia (IDA) during pregnancy. Data on prevalence of IDA in pregnant women are lacking in Australia. However, estimates indicate that between 4-20 % of women have low iron stores and IDA is more common in Aboriginal women than in non-Aboriginal women(12). Changes in iron absorption during pregnancy means that iron supplementation may not be required for all pregnant women. Monitoring blood levels of iron during pregnancy and intervening with iron supplements when necessary will help ensure adequate iron is maintained during pregnancy.
Listeria infection can be caused by eating foods contaminated with the bacteria called Listeria monocytogenes. Pregnant women are at risk of Listeria infection, which can cause miscarriage, still birth, premature birth or a very ill infant at birth. High risk foods for Listeria infection include:
Pre-cooked meat products eaten without further cooking (e.g. pate, sliced deli meat, chicken, smoked fish, smoked mussels, oysters and raw seafood, prepared salad including fruit salads and coleslaw, unpasteurised dairy products and soft cheese products such as camembert, ricotta and brie, soft serve ice-cream).
It is recommended that pregnant women avoid these high-risk foods and ensure safe handling practices when preparing food(13).
There are health benefits associated with including fish in the diet and pregnant women can still include fish as part of a healthy diet. However, mercury, which can be found in fish, can impair the development of the nervous system in the foetus if consumed in high levels. FSANZ provides guidelines and recommendations for the amount and types of fish that can be eaten by women during pregnancy. Pregnant women should:
“eat shark (flake), broadbill, marlin and swordfish no more than once a fortnight and should not eat any other fish during that fortnight. Orange roughy and catfish should be eaten no more than once a week, and no other fish should be eaten during that week.”(14)
A well planned vegetarian diet can support appropriate nutritional health during pregnancy. Vegetarian women frequently consume more fibre, wholegrains, and lower fat diets than non-vegetarian women. Care needs to be taken to ensure meat products are replaced with appropriate alternatives such as legumes, beans and wholegrains to help meet the additional protein iron and zinc needs. Foods such as tofu, eggs and low fat dairy products are nutrient rich and can help to meet nutrient needs during this time. However, it is difficult for women following a vegetarian eating pattern to eat sufficient vitamin B12 for health and supplements should be considered.
The NHMRC recognises that alcohol consumption can harm the developing foetus or breastfeeding baby. While the effects of heavy drinking during pregnancy are well accepted, there is no lower limit of intake that can be recognised generally as being safe. As a result, avoiding alcohol during pregnancy is the safest option. Therefore, the NHMRC recommend “for women who are pregnant or planning a pregnancy, not drinking alcohol is the safest option”(15).
Consuming too much caffeine during pregnancy is associated with a reduced birth weight or foetal growth restriction(16). Australia does not currently have a nationwide recommendation on the amount of caffeine considered safe during pregnancy but some States and Territories adopt the UK recommendation of limiting caffeine intake to 200mg/day(17). Common sources of caffeine in the Australian diet include coffee (~100mg caffeine in a medium brewed coffee), tea (~36mg caffeine in a medium tea), cola beverages (~35mg caffeine in a 375ml can). However, ‘energy drinks’ contain more caffeine (~114mg in a 355ml Red Bull).
Some women experience a loss of appetite or aversion to particular foods during their pregnancy. Both of these are more common during the first trimester of pregnancy but can occur throughout pregnancy. It is important to work with the food likes and dislikes while trying to follow the recommendations presented in the dietary guidelines.