Increased nutrient needs
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.
The Nutrient Reference Values (NRVs) 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 these additional needs 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(2).
Weight gain during pregnancy
The amount of weight gained during pregnancy is important for the short term and long term health of both the mother and the baby. Measuring weight gain during pregnancy is a simple and effective way to determine if energy intake is meeting the needs for appropriate growth. 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 (IOM) 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 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. These increased needs are easily met by current dietary patterns. Dietary sources of protein include cereals and lean meats and alternatives. Protein supplements are not recommended during pregnancy.
Recommended dietary intake of protein during pregnancy(1):
Woman 19-50 years: 0.75gm/kg body weight
Pregnant women 19-50 years: 1.00gm/kg body weight
Fatty acid requirements
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. These recommendations have been established based on median population intakes within Australia.
Recommended dietary intake of omega-3 fatty acids during pregnancy (1):
Women 14-18 years: 85mg/day
Pregnant women 14-18 years: 110mg/day
Women 19-50 years: 90mg/day
Pregnant women 19-50 years: 115mg/day
Due to the changes within the gastrointestinal tract and increased 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. 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.
Recommended dietary intake of fibre during pregnancy (1):
Women 14-18 years: 22g/day
Pregnant women 14-18 years: 25g/day
Women 19+ years: 25g/day
Pregnant women 19+ years: 28g/day
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.
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|
|Vitamin C||45mg/day||60mg/day||Fruit, vegetables|
|Vitamin A||700μg/day||800μg/day||Red, yellow vegetables, dairy products, vegetable oils|
*Nutrient Reference Values(1)
Folate is a B vitamin required for the production of red blood cells, cell division and for the healthy development of the neural tube. Folate can be found in dark leafy green vegetables, lentils and legumes, avocados, oranges, strawberries and some fortified breads and cereals. Folic acid is the synthetic form of the vitamin, which is used in supplements and food fortification, and has greater bioavailability. For this reason, folate is measured in micrograms (µg) dietary folate equivalent (DFE).
1 µg dietary folate equivalent = 1 µg food folate
= 0.5 µg folic acid on an empty stomach
= 0.6 µg folic acid with meals or as fortified foods
The RDI for folate is increased during pregnancy. The literature suggests that pregnant women consume at least 400 to 800µg DFE per day for healthy maternal, placental, and foetal tissue growth(6). In Australia, the RDI for pregnant women is set at 600µg DFE/day, which may be challenging for women to meet without the use of fortified foods or supplements. Following implementation of mandatory fortification, the average folic acid intake for women of child bearing age is now 247μg/day (or 460µg DFE)(7).
It is well recognised 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).
As such, there are also separate recommendations for women to have 400-500μg/day of folic acid for those planning a pregnancy and during for the first 3 months of pregnancy(8,9). 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 folate during pregnancy(1):
Women 19-50 years: 400µg DFE/day
Pregnant women 19-50 years: 600µg DFE/day
Supplementation recommendation: 400-500µg/day of folic acid pre-conception and during the first 3 months of pregnancy(8,9)
Choline is an essential nutrient(10). Folic acid assists in preventing neural tube defects, and choline supports folic acid in this role by contributing to normal homocysteine metabolism.
Whilst there is no NRV set for choline in Australia, it has been recommended that choline intake should increase from 425 mg/day in non-pregnant women to 450 mg/day in pregnant women(11). Choline can be synthesised by the body, but this is not sufficient enough to meet requirements. Due to the increased needs during pregnancy and lactation it is recommended mothers increase their choline consumption through either diet or supplementation. Good dietary sources include red meat, eggs, fish, soybean, potatoes and mushrooms.
Vitamin D is essential for bone health and development by assisting with calcium and phosphate absorption(9). While the requirements for Vitamin D do not increase, it is important for at risk women to be screened for vitamin D deficiency during pregnancy(9). The current recommendations for supplementation and routine screening for Vitamin D are conflicting, therefore medical professionals should use discretion with each patient (1,9,12). Vitamin D is primarily produced in the body following sunlight exposure, with limited amounts available in some foods.
Recommended Dietary Intake of vitamin D during pregnancy(1):
Women 19-50 years: 5µg DFE/day
Pregnant women 19-50 years: 5µg DFE/day
The NRV recommends that pregnant women consume 27mg/day of iron during pregnancy(1). This level of iron intake can be challenging to achieve through dietary intake alone. Therefore, monitoring iron status during pregnancy is important help to identify women at risk of low iron who may benefit from iron supplementation. If iron deficiency anaemia is diagnosed during pregnancy, supplementation of at least 60mg/day is recommended(9). Iron can be found in red meat and poultry, as well as smaller amounts in fish, green leafy vegetables, and legumes such as lentils and beans. Plant sources of iron should be consumed with vitamin C rich foods to optimise absorption.
Recommended Dietary Intake of iron during pregnancy(1):
Women 19-50 years: 18mg/day
Pregnant women 19-50 years: 27mg/day
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. Rich sources of calcium include milk, dairy products and calcium fortified alternatives such as soy milk. Women with insufficient calcium intake should take a calcium supplement of at least 1000mg/day(9).
Recommended Dietary Intake of calcium during pregnancy(1):
Women 19-50 years: 1000mg/day
Pregnant women 19-50 years: 1000mg/day
It appears that current intakes of zinc are close to the recommended levels needed during pregnancy. The additional servings of grain (cereal) foods and lean meats and alternative food groups will help meet these increased requirements (2). Rich sources include beef, chicken, eggs and fish, as well as milk, cheese, lentils and legumes.
Recommended Dietary Intake of zinc during pregnancy(1):
Women 19-50 years: 8mg/day
Pregnant women 19-50 years: 11mg/day
Iodine requirements increase 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 (13). Iodine can be found in foods such as fortified bread products, shellfish (well cooked), iodised salt, eggs and sea vegetables.
It is also recommended that women who are pregnant, breastfeeding or considering pregnancy take an iodine supplement of 150µg/day(13). Women with pre-existing thyroid conditions should consult with their doctor prior to supplementation.
Recommended Dietary Intake of iodine during pregnancy(1):
Women 19-50 years: 150μg/day
Pregnant women 19-50 years: 220μg/day
Sodium and potassium during pregnancy
In order to reduce the risk of dietary related chronic diseases such as high blood pressure, people aged over 14 years should consume no more than 600mg of sodium per day(1). 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(1). Increasing intakes of fruits, wholegrains, vegetables and dairy products will improve potassium intakes. The best approach to limit sodium intake and optimise potassium intake is to limit processed and packaged foods and choose whole foods wherever possible.
- National Health and Medical Research Council (NHMRC). Nutrient reference values for Australia and New Zealand: including dietary recommended intakes. Canberra, Australia: NHMRC publications, 2006.
- National Health and Medical Research Council (NHMRC), (2013). Australian Dietary Guidelines.
- Institute of Medicine (IOM), National Research Council (NRC) (2009). Weight gain during pregnancy: Re-examining the guidelines. Washington, DC: The National Academies Press. External link
- Crane J.M, White J, Murphy P, et al., (2009). The effect of gestational weight gain by body mass index on maternal and neonatal outcomes. J Obstet Gynaecol Can. 31(1), 28-35. External link
- Callaway L.K, Prins J.B, Chang A.M, McIntyre H.D (2006). The prevalence and impact of overweight and obesity in an Australian obstetric population. Med J Aust. 84(2), 56-9. External link
- Irvine N, England-Mason G, Field C.J, Dewey D, Aghajafari F (2022). Prenatal Folate and Choline Levels and Brain and Cognitive Development in Children: A Critical Narrative Review. Nutrients 2022, 14, 364.
- Australian Institute of Health and Welfare (2016). Folic acid & iodine fortification. [Cited Feb 2022]. External link
- Australian Government: Department of Health (2021). Pregnancy Care Guidelines: Nutrition and physical activity. [Cited Feb 2022]. External link
- The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) (2019). Vitamin and Mineral supplementation and pregnancy. [Cited Feb 2022]. External link
- Zeisal, SH. da Costa, KA (2009). Choline: an essential nutrient for public health. Nutrition Reviews, 67(11): 615 - 623.
- National Institutes of Health (2021). Choline: Fact Sheet for Health Professionals. [Cited Feb 2022]. External Link
- The Royal Women's Hospital (2020). Vitamin D testing and Management- Maternity patients and newborns. [Cited Feb 2022]. External Link.
- National Health and Medical Research Council (2010). NHMRC Public Statement: Iodine supplements: National Health and Medical Research Council [cited Feb. 2022].