There are a range of adverse health effects associated with maternal under-nutrition. It can affect both the pregnant woman and developing baby in the short and long-term.
Under-nutrition can be classified as either:
Malnutrition occurs when an individual consistently consumes less energy (measured in calories and obtained from proteins and carbohydrates) than they expend. Malnutrition results in the individual being underweight and experiencing greater ill-health.
Micronutrient deficiency is a condition which occurs when an individual consumes enough food overall, but does not consume enough of the specific micronutrients they need to maintain the growth and function of specific body parts and systems. For example, calcium deficiency can affect the growth of bones and teeth.
A woman's nutritional status at the time she becomes pregnant influences her health during pregnancy and the health of her baby. It is determined largely by her nutritional intake before pregnancy. If a woman is under-nourished prior to conception because she does not eat enough, she may be malnourished and underweight at the time she conceives. This will have an ongoing effect on her nutritional status throughout the pregnancy. Her nutritional status at the time she becomes pregnant is also an important factor influencing the health of the foetus, as well as the long term health of the infant.
For more information, see Importance of Nutrition Before Pregnancy.
Health risks for the mother
Women who are under-nourished (have a BMI of <18.5kg/m2) at the time of conception are unlikely to improve their nutritional status during pregnancy, when their bodies have additional demands due to the growing baby. They may fail to gain sufficient weight during pregnancy and have a higher risk of maternal mortality (dying whilst pregnant) than normal weight women.
Health risks for the foetus and newborn baby
Under-nourished women may also lack the nutritional stores required to support embryo growth. Embryo refers to a fertilised egg, before it begins to take on human characteristics (at which stage it is referred to as a foetus). In the first few days after conception the embryo exists in the woman's womb but has not yet implanted into the lining of the womb where it will grow throughout the pregnancy. This is known as the pre-implantation period and is the period of pregnancy in which cells divide and replicate most rapidly. Maternal malnutrition can adversely affect the division and replication of cells in the embryo at this stage, impairing its development. Impaired embryo development in turn adversely effects the development of the foetus in the later stages of pregnancy.
A woman's nutritional status at the time she becomes pregnant also influences the differentiation of cells in the embryo into foetal and placental cells. When the embryo implants into the wall of a woman's uterus, it develops two types of cells, those that will become the foetus and those which will become the placenta (the structure which nourishes and supports the foetus during pregnancy). In undernourished women, a greater number of cells are likely to form the placenta compared to the foetus, meaning that the foetus begins its life smaller than it should do. This can lead to restricted foetal growth and increases the risk of the baby being born at a low-birth weight (<2.5kg). Low birth weight is in turn associated with a range of adverse outcomes in childhood and later in life.
Foetal development is also affected by maternal nutritional status before pregnancy. It is during the first five weeks of pregnancy when the foetus develops most of its organs (e.g. heart, brain, lungs). At this stage the foetus is most vulnerable to the mother's malnutrition. Nutritional deficiencies at this time may retard the growth of the foetus's organs. As the woman is usually unaware she is pregnant at this early stage, she can only ensure she is well nourished by eating properly before she becomes pregnant.
Health risks for the child in the long term
When a foetus is malnourished in the early (and later) stages of pregnancy it may also have a lifelong programming effect which predisposes the baby to chronic health conditions later in life. For example, the foetus may adapt its metabolism to cope with malnutrition by reducing the amount of insulin and glucose produced. Such adaptation has been shown to permanently program the metabolic system and increase the risk of chronic health conditions later in life such as type 2 diabetes.
Micronutrient status at the time of conception is also determined by historic nutrient consumption, and deficiency in one or more micronutrients can detrimentally affect the health of the mother and her baby.
Health risks for the mother
Women who experience deficiencies in specific micronutrients before pregnancy have an increased risk of the following health conditions:
Foetal and neotnatal health risk
Maternal deficiency in particular micronutrients can also affect the development and health of the foetus. For example:
Folate deficiency in early pregnancy is associated with deficits in the development of the neural tube (the tube from which the brain and spinal cord develop) which may result in conditions such as spina bifida. Folate status in early pregnancy depends on preconception nutrition;Calcium deficiency which restricts foetal skeletal development may occur if a woman does not have adequate calcium stores in her bones (developed through long-term calcium consumption), from which the foetus can receive this important micronutrient; andIron deficiency which causes maternal anaemia is associated with intrauterine growth retardation (restricted foetal growth) and low birth weight. Iron deficiency can also affect the absorption of folate. As folate absorption is most critical in the early stages of pregnancy, ensuring adequate preconception iron status is also important.
Health risks for the child in the long-term
The effects of pre-pregnancy micronutrient deficiency may be long term. For example, neural tube defects often cause life long health conditions such as spina bifida. Those born at low birth weight have an increased risk of impaired physical and mental development. They may grow shorter than and have more learning difficulties than babies born at a healthy weight (?2.5kg).
Health risks for the mother
Pregnant women who receive inadequate nutrition experience greater maternal morbidity (are more likely to be ill whilst pregnant) and have a higher risk of poor pregnancy outcomes (e.g. premature birth, miscarriage). They also have an increased risk of developing the following conditions:
Health risks for the foetus and newborn baby
Under-nutrition in pregnant women is associated with a range of detrimental effects to the developing foetus, including intrauterine growth retardation (under-growth) and low-birth weight. Maternal under-nutrition during pregnancy, IUGR and low birth weight are in turn associated with a range adverse outcomes for the developing foetus and/or newborn baby, including an increased risk of:
Health risks for the child in the long-term
As mentioned above, maternal under-nutrition causes metabolic and other changes in the foetus, which program its metabolic responses following birth. For example, a foetus that is malnourished adapts by reducing insulin and glucose production. This is thought to program and permanently alter the individual's glucose and insulin metabolism throughout their life and increase the risk of chronic nutritional disorders including type 2 diabetes mellitus, metabolic syndrome and obesity. For example, one study showed that the lower the birth weight of an infant, the higher the risk of developing type 2 diabetes. Men who were born at a very low weight were seven times more likely to develop diabetes compared to men born at a high weight.
However, the effects of maternal under-nutrition vary depending on the stage of pregnancy at which under-nutrition is experienced. For example, one study reported that exposure to maternal malnutrition in the first trimester of pregnancy was associated with an increased risk of obesity and coronary heart disease, while malnutrition in the second or third trimester was associated with poor glucose metabolism.
The offspring of women who experienced under-nutrition during pregnancy have an increased risk of developing:
Individuals who are born at a low weight have a greater risk of poor development outcomes during infancy and childhood. The mother's nutritional intake before, during and after pregnancy influences their child's immediate and long-term mental development and performance.
The greatest brain growth occurs between the 3 months before birth and 2 years of age. It is at these stages that the development of the brain's nerve system and the connection between nerves is at its peak and so the brain requires the most energy to maintain its growth. The nerve system made during this time impacts the way the brain is structurally and functionally organised (cortical organisation) throughout life.
Poor foetal development has been associated with the following adverse health and development outcomes later in life:
Poor performance at school, learning and developing skills;Reduced ability to perform physical work; andReduced economic productivity.There are also numerous maternal and foetal health risks associated with micronutrient deficiency during pregnancy, that is, deficiency in particular micronutrients such as folate, and vitamin B12.
Health risks for the mother
Maternal health risks which may arise as a result of deficiency in particular micronutrients include:
Health risks for the baby
A woman's deficiency in particular micronutrients whilst she is pregnant has detrimental effects on particular aspects of foetal development.
Foetal health risks which arise as a result of deficiency on particular micronutrients include:
For more information about pregnancy, including preconception advice, stages of pregnancy, investigations, complications, living with pregnancy and birth, see Pregnancy.
For more information on nutrition, including information ontypes 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.
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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