Nutrition and pregnancy


Maintaining a healthy balanced diet is important for maintaining optimal health throughout life. For women of childbearing age, good nutrition is important for preparing the body for the demands of pregnancy.

During pregnancy, a woman’s macronutrient (energy) and micronutrient (e.g. vitamins, mineral) requirements increase, and it is even more important that she consumes food which will give her both the energy and the specific micronutrients which are essential for maintaining her and her growing baby’s health. For example, women require an additional 240 calories of energy per day in the second trimester and 452 calories per day in the third trimester of pregnancy to account for foetal growth. An additional 975 milligrams of iron is required in the course of the pregnancy to form foetal and additional maternal blood.

While nutritional supplements can provide large quantities of particular micronutrients, a healthy balanced diet should form the basis of a woman’s nutritional intake. Good nutrition is most important immediately prior to conception and during the first 12 weeks of pregnancy (including the very early stages, when the woman is unaware she is pregnant). It is therefore important for women to maintain a healthy diet throughout their childbearing years, and particularly if they are planning to become pregnant.

Why maintain a healthy diet before and during pregnancy

Maintaining a healthy diet before and during pregnancy helps to protect both the pregnant mother and her developing baby from immediate and long-term health risks.

Importance of a healthy diet before becoming pregnant

Nutrition and pregnancyA woman’s nutritional status during pregnancy depends on the availability of nutritional reserves, that is, stores of particular micronutrients such as calcium and iron, which have been built up in her body from prior consumption of foods containing those micronutrients. As these reserves build up before a woman becomes pregnant, maintaining good nutrition prior to conception is vital for ensuring adequate nutritional status during pregnancy. Women who are underweight or overweight, or who have deficiencies in particular micronutrients rarely “catch-up” by improving their diet once they are pregnant, as at this stage their body already faces additional nutritional demands because of the growing baby.

Maintaining a healthy diet prior to conception is also important because the ongoing development of the baby depends on the health of the embryo from which it is formed. The embryo is the name of the first cells which reproduce when a sperm and egg meet and conceive. The embryo then implants in the wall of the woman’s uterus (womb) and goes on to divide into two types of cells; those that form the foetus and those that form the placenta (which provides nutrition to the foetus during pregnancy). Evidence suggests that maternal nutritional status has an important influence on the proportions of cells which go on to form the foetus and placenta. In undernourished women (women who do not consume enough energy or calories), a greater proportion of cells are likely to form the placenta compared to the foetus, which means the foetus will be relatively small when it begins growth and its development in the womb will be restricted. This increases the likelihood that the baby will be too small (weigh less than 2.5kg) when it is born.

Not consuming enough of particular micronutrients can also retard foetal development in the early stages of pregnancy. In particular, there is strong evidence of an association between folate deficiency and deficits in the development of the neural tube.

Importance of a healthy diet during pregnancy

Nutrition and pregnancyPoor maternal nutrition is the key factor contributing to poor foetal development, which increases the risk that the baby born will be ill or die. Research shows that maternal nutritional status during pregnancy plays a more important role in determining foetal health and predisposition to some diseases, than genetic factors (e.g. a genetic predisposition to obesity). For example, studies show that in gestational surrogacy (where one woman bears a child conceived from the egg of another woman), factors relating to the recipient mother (the woman bearing the child) influence foetal health more so than those of the donor mother (the woman whose eggs were used).

Maternal nutrition during pregnancy also appears to have a “foetal programming” effect, that is, the foetus learns nutritional habits, which will influence it for the rest of its life, before it is even born. A foetus will also adapt its metabolism and other body systems to cope with different states of nutrition. For example, an under-nourished foetus, which does not receive enough macronutrients or energy, responds by reducing glucose and insulin production, which ultimately slows the rate of foetal growth and increases the risk of low birth weight. It may also alter the metabolism permanently and leave an individual predisposed to metabolic conditions such as diabetes. The foetus also adapts to under-nutrition by redirecting blood flow and therefore the supply of nutrients to protect the brain, at the expense of fully developing other organs including the kidneys, muscles and endocrine system (the system which regulates the body’s hormone production).

The nerves which regulate the foetus’s appetite are also programmed while it is developing in the womb and this affects an individual’s appetite regulation later in life. The foetal programming effect influences not only how much an individual consumes, but also their food preferences. Individuals who are programmed to consume high-fat, high-sugar diets in utero (whilst in the womb), also have a greater tendency to consume such diets throughout their life.

Women at risk of poor nutrition

All women experience increased nutritional requirements during pregnancy, and thus all women should ensure they are well informed about and attempt to maintain a healthy balanced diet before and during pregnancy. However, some women may find it harder to access or consume all the necessary components of a healthy diet throughout their life and during pregnancy. For example, those who are food insecure may be unable to access enough food to nourish themselves and their baby.

Nutrition and pregnancyWomen should also be aware that poor nutrition results from a complex range of factors, of which nutritional intake is just one. Infectious disease, physical labour and adolescent growth all create nutritional demands which may mean that a diet which meets the needs of a normal healthy woman is insufficient for a growing adolescent, a woman who is ill or one who engages in physical labour during pregnancy.

Lifestyle habits such as smoking and drug use can limit the extent to which the body absorbs and uses nutrients and so these behaviours increase the risk of poor nutritional status during pregnancy.

Women who have an increased risk of experiencing poor nutrition during pregnancy include:

  • Vegan and vegetarian women, as many micronutrients are largely sourced from animal derived foods;
  • Aboriginal and Torres Straight Islander women, who are predisposed to poor nutrition due to socioeconomic and demographic factors such as poverty and food insecurity;
  • Women of low socioeconomic status who generally have poorer nutrition and health and are more likely to give birth to a low birth weight infant;
  • Women with health conditions including diabetes and infectious conditions which create additional nutritional demands on the body;
  • Women who have recently given birth, as short birth intervals do not give a woman’s body the chance to recuperate and build up nutritional stores between pregnancies;
  • Women with multiple pregnancies (twins, triplets, etc.) which place greater nutritional demand on the pregnant woman’s body;
  • Women exposed to stress, as this can increase nutrient losses and change eating patterns;
  • Women who smoke, consume alcohol or take illicit drugs as these can increase nutrient losses and change eating patterns;
  • Adolescent women as their bodies are still growing and require nutrients to sustain their growth. As such, the growing foetus competes with the growing adolescent body for nutrients;
  • Women with severe nausea or vomiting during pregnancy (known as hyperemesis gravidarum), a condition which occurs in 1-2% of pregnancies and typically occurs beyond 16 weeks gestation.

Women who find it difficult to access food should seek help from a health professional or support group. For example, those from low socioeconomic backgrounds who have difficulty accessing food should seek assistance from an agency which helps people access food. Those with special eating requirements (e.g. lactose intolerance) may need individual nutritional advice from their GP, a nutritionist or dietian. Women who have deficiencies in particular micronutrients may also require nutritional supplements during pregnancy.

More information on Nutritional Supplements During Pregnancy.

More information

Pregnancy For more information about pregnancy, including preconception advice, stages of pregnancy, investigations, complications, living with pregnancy and birth, see Pregnancy.
Nutrition For more information on nutrition, including information on types and composition of food, nutrition and people, conditions related to nutrition, and diets and recipes, as well as some useful videos and tools, see Nutrition.
Pregnancy planning For more information about pregnancy planning, including importance of nutrition before pregnancy, being under-weight, being overweight, tobacco exposure and alcohol consumption, see Pregnancy Planning (Preconception Advice).


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