Food requirements during pregnancy

Good nutrition is important for both a mother and her developing infant, so the baby has the best start to life. Within Australia and New Zealand, 2 public health documents provide evidence based food and nutrient recommendations for healthy populations: the Nutrient Reference Values (NRV)(1) and the Australian Dietary Guidelines (ADG)(2). Maintaining a healthy diet during pregnancy can largely be achieved through appropriate food choices, but supplements for some nutrients are recommended.

The Australian Dietary Guidelines(1) provide recommendations for the types and amounts of foods to consume during pregnancy. These recommendations are designed to help women achieve intakes of the nutrient recommendations described below, with the exception of iron. Following an eating pattern consistent with the recommendations below will help pregnant women to meet their nutrient needs.

The healthy eating guide during pregnancy, developed by the NHMRC provides simple and easy to follow recommendations for pregnant women (Table 1).

Table 1: Recommended dietary patterns for adult and pregnant women aged 19-50 years(2)

Vegetables & LegumesFruitGrain (cereal) foods, mostly wholegrainLean meat, poultry, fish, eggs, tofu, nuts/seeds & legumesMilk, yoghurt, cheese &/or alternativesExtra foods
Girls 14-18 yr5270-2½
Pregnant 14-18 yr5280-3
Adult women5260-2½
Pregnant women520-2½

Nutrient needs during pregnancy

Increased energy needs

Women need additional energy in the 2nd and 3rd trimester to support the growth demands of the baby. The additional energy needed is modest and most women can easily meet this from small increases in food intake.

NRVs recommend an additional 1,400 kJ/day in 2nd trimester and an additional 1,900 kJ/day in the 3rd trimester. Overweight or obese women starting pregnancy will need less than this and underweight women need more (an additional 150 kJ/day).

The ADG have translated these extra needs into recommended food patterns and highlight this extra energy should come from 2½ extra servings of grain (cereal) foods and 1 extra serving from the lean meats and alternatives food group. Measuring weight gain routinely during pregnancy allows monitoring of whether energy intake is meeting appropriate growth requirements.

Protein needs

Protein needs increase during the 2nd and 3rd trimesters (Table 2), which should generally be achieved via dietary intake. Protein supplements are not recommended during pregnancy.

Table 2: Protein needs during pregnancy(1)  

NutrientRDI Woman (14-18 yr)RDI Pregnant (14-18 yr)RDI Woman (19-50 yr)RDI Pregnant (19-50 yr)Foods
Protein0.77 g/kg1.02 g/kg0.75 g/kg1.0 g/kgWide spread in most
foods. Recommended increased protein via
grain and lean meats/alternatives

Increased fibre needs

Increased fibre is recommended during pregnancy, because gastrointestinal tract and renal water reabsorption changes that occur during pregnancy can result in constipation. Vegetables, wholegrains, beans, legumes and fruit are good sources of resistant starch prebiotic fibre, soluble fibres and insoluble fibres, and following a dietary pattern recommended in the Australian Dietary Guidelines will help pregnant women meet increased needs.

Increased Fatty Acid needs

Essential fatty acids are needed 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 fatty fish, eggs, lean meats, nuts and seeds and their associated oils.

The NRVs recommend an Adequate Intake (AI) of long chain essential fatty acids of 90 mg day for an adult woman (140mg/day for a teenage woman 14-18 years) and this increases to 115 gm day during pregnancy (110 mg for a teenage woman) to account for the extra needs in the developing foetus. These recommendations have been established based on median population intakes within Australia.

Vitamin Needs

The amount of water soluble vitamins needed during pregnancy generally increases: for the fat soluble vitamins, only Vitamin A needs increase. Most of these increased pregnancy needs can be met by increasing the amount of food recommended in the Australian Dietary Guidelines, except folate.

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 a pregnant women is 600 µg/day (Table 3), which may be challenging to meet without the use of fortified foods. In addition, increased folate (in the form of folic acid) during pregnancy can reduce the risk of having a baby with a neural tube defect (NTD)(3).

For folate, supplementation is recommended(1). Thus, dietary supplementation with a dose of 500 micrograms/day folic acid is recommended, from at least one month before conception and during the first 12 weeks of pregnancy. A woman at increased risk of having a baby with a NTD (that is a woman who has previously had a baby with a NTD or who has a close relative with a baby with a NTD) is recommended to consume 5 mg of folic acid daily(1) .

Table 3: Nutrient reference values pre-pregnancy, during pregnancy and lactation(1)

Protein (g)Fibre (g)Folate (ug)Vit A (ug)Vit C (mg)Vit D (ug)Calcium (mg)Zinc (mg)Iron (mg)Iodine (ug)Selenium (ug)
Pre-pregnancy4625600700455100081815060
Pregnancy58-6028600700-80055-6051000-130010-112722065
Lactation63-6730500110080-8551000-130011-129-1027075

The need for some, but not all, minerals increase during pregnancy (Table 4)(1).

Iodine

Iodine requirements increase to 220 µg/day during pregnancy due to the increased production of thyroid hormones. This iodine intake is difficult to meet with food alone and dietary intake plus supplementation is recommended. The NHMRC recommendation for iodine is that all women who are pregnant, breastfeeding or considering pregnancy should take an iodine supplement of 150 micrograms (μg) each day(4).However, that women with pre-existing thyroid conditions should seek advice from their medical practitioner prior to taking a supplement.

The foetus requires iodine for normal brain and nervous system development. Mild to moderate iodine deficiency can cause learning difficulties and affect physical development(5). Iodine can be found in foods like fortified bread products, shellfish, iodised salt, eggs and sea vegetables. In 2009, Australia and New Zealand introduced mandatory fortification in bread making to improve the iodine status of the population(6). Since then, 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 88 µg/L in 2008 (pre-fortification) to 145 and 166 µg/L in 2011 and 2012 respectively. They further observed that women who were taking iodine supplements had significantly higher iodine levels than women not taking supplements (178 and 202 µg/L compared with 109 and 124 µg/L 2011 and 2012 respectively)(7).

Iron

The NRVs recommend pregnant women consume 27 mg/day iron during pregnancy. This level of iron intake is challenging to achieve via dietary intake alone. Monitoring iron status during pregnancy is important help to identify women at risk of low iron who may benefit from iron supplementation.

Calcium

There is no recommendation to consume additional calcium during pregnancy. This is because there is a significant increase in a mother’s ability to absorb and retain calcium during pregnancy. These adaptations work to provide sufficient calcium necessary for foetal growth without requiring an increase in maternal dietary intake or 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.

Zinc

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 meats and alternatives during pregnancy will help to meet these increased zinc needs as these foods are good sources of zinc.

Sodium and Potassium

The NRV recommend that people over the age of 14 years consume no more than 600 mg/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 select foods low in salt (ideally less than 120 mg/100 g but no more than 500 mg/100 g) 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 320 mg/day of potassium, these recommendations also apply to pregnant women. Increasing intakes of fruits, wholegrains, vegetables and dairy products will improve potassium intakes.

Weight gain during pregnancy

The amount of weight gained during pregnancy is important for the short- and long-term health of both the mother and the baby. As a guide, between 1-2 kg weight gain during the 1st trimester and ~0.5 kg/week for the remaining 2 trimesters is ideal. The US Institute of Medicine recommends the following weight gain during pregnancy (Table 2)(8).

Table 4: Recommendations for weight gain during pregnancy(8)

Pre-pregnancy BMI (kg/m²) Recommended weight gain (kg)
< 18.512½ - 18
18.5 to 24.911½ - 16
25 to 29.97 - 11½
>305 - 9

Ideally, women planning a pregnancy should achieve a healthy body weight before becoming pregnant. Weight reduction for overweight or obese women is not recommended during pregnancy, but the amount of weight gain should be lower compared with women entering pregnancy at a normal (8). It is recommended that underweight women (i.e. BMI <18.5) gain more weight to help ensure a healthy birth weight for the infant.

Nutritional concerns

Iron Deficiency Anaemia

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(9). Changes in iron absorption during pregnancy mean that iron supplementation may not be required for all pregnant women. Monitoring blood levels of iron and intervening when necessary with iron supplementation is necessary to ensure adequate iron is maintained during pregnancy.

Listeria

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 cheeses such as camembert, ricotta, brie and soft serve ice-cream. It is recommended that pregnant women avoid these high-risk foods and ensure safe handling practices when preparing food(10).

Mercury

Including fish in the diet comes with health benefits 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.”(11).

Vegetarian diets and pregnancy

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 a women following a vegetarian eating pattern to eat sufficient vitamin B12 for health, and supplements should be considered.

Alcohol

The NHMRC recognise 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 generally recognised as 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(12).

Caffeine

Consuming too much caffeine during pregnancy is associated with a reduced birth weight or foetal growth restriction(13). The recommended caffeine limit in Australia during pregnancy is a maximum of 200 mg/day. This would be equivalent to 1 cup of strong espresso style coffee, 3 cups of instant coffee, 4 cups of medium strength tea, 4 cups of cocoa or hot chocolate or 4 cans of cola(14). These amounts are estimates because the amount of caffeine in coffee particularly, varies widely. Common sources of caffeine in Australian diet include coffee (~100mg caffeine/medium brewed coffee), tea (~36mg caffeine/medium tea), cola drinks (~35mg caffeine/375ml can), with energy drinks containing more caffeine (114mg/355ml red bull).

Food aversions and pregnancy

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 at throughout. It is important to work with the food likes and dislikes to try and follow the recommendations presented in the dietary guidelines.

References

  1. National Health and Medical Research Council. Nutrient reference values for Australia and New Zealand: including dietary recommended intakes. Canberra, Australia: NHMRC publications, 2006.
  2. National Health and Medical Research Council. Australian Dietary Guidelines. Canberra: National Health and Medical Research Council, 2013.
  3. The Royal Women’s Hospital. Guideline – Folate in Pregnancy. [cited April 2019]. https://thewomens.r.worldssl.net/images/uploads/downloadable-records/clinical-guidelines/folate-in-pregnancy_150517.pdf
  4. National Health and Medical Research Council. NHMRC Public Statement: Iodine supplements. National Health and Medical Research Council; 2010. [cited April 2019]. Available from: http://www.nhmrc.gov.au/_files_nhmrc/publications/attachments/new45_statement.pdf
  5. World Health Organisation. Iodine Status Worldwide. WHO Global Database on iodine deficiency 2004 [cited April 2019]. Available from: http://whqlibdoc.who.int/publications/2004/9241592001.pdf
  6. Food Standards Australia and New Zealand. Standard 2.1.1 – Cereals and Cereal Products, Australian New Zealand Food Standards Code. Canberra: Australian Government, 2009.
  7. Charlton KE, et al. Improvement in iodine status of pregnant Australian women 3 years after introduction of a mandatory iodine fortification programme. Preventive Med. 2013;57(1):26-30.
  8. Institute of Medicine (IOM), National Research Council (NRC). Weight gain during pregnancy: Reexamining the guidelines. Washington, DC: The National Academies Press, 2009.
  9. Pasricha SR, et al. Diagnosis and management of iron deficiency anaemia: a clinical update. Med J Aust. 2010;193(9):525-32.
  10. Food Standards Australia and New Zealand. Listeria 2011. [cited April 2019]. Available from: http://archive.foodstandards.gov.au/consumerinformation/listeria/listeriabrochuretext.cfm
  11. Food Standards Australia and New Zealand. Mercury in Fish 2011 [cited April 2019]. Available from: http://www.foodstandards.gov.au/consumer/chemicals/mercury/Pages/default.aspx
  12. National Health and Medical Research Council. Australian guidelines to reduce health risks from drinking alcohol. Canberra: National Health and Medical Research Council.
  13. CARE Study Group. Maternal caffeine intake during pregnancy and risk of fetal growth restriction: a large prospective observational study. BMJ. 2008;337:a2332. Epub 2008/11/05.
  14. NSW Medications in Pregnancy and Breastfeeding Service. The Royal Hospital for Women. [cited April 2019]. Available from: https://www.seslhd.health.nsw.gov.au/sites/default/files/migration/Mothersafe/documents/Caffeinenov27.pdf