The Importance of Good Nutrition during Pregnancy

The nutritional needs during pregnancy are increased to meet the high metabolic demands of the growing foetus as well as due to the physiological changes in the mother who is to carry the child and prepare for lactation.1  Various physiological adaptations during this period may help shield the foetus from the insufficiencies in the maternal diet.2  However, these insufficiencies may affect the short and long-term development and health of the foetus and the infant with resultant unfavourable changes in weight, size, body composition, birth defects or even metabolic competence resulting in a disease in later life.2,3

A healthy pregnancy is without physical or psychological pathology in the mother and results in the delivery of a healthy baby.4Multiple factors may affect nutrition during pregnancy. These include:3

  • Malnutrition or obesity before conception
  • Maternal age (adolescents or age >35 years)
  • Chronic diseases
  • Multiple pregnancies
  • Substance abuse
  • Nutritional disorders such as bulimia or anorexia
  • Reduced physical activity or a sedentary lifestyle

Effects of Preconception Nutrition

Categorically stating nutrition is one of the cornerstones of health.  Sufficient maternal nutrition can critically modulate the development of the foetus thus reducing the risk of birth defects.5

Undernourishment or obesity prior to conception can lead to a variety of adverse outcomes compared to women with normal weight.3  Maternal malnutrition is a risk factor for low-birth weight infants or small-for-gestational age infants, premature birth, or foetal growth retardation.  This may result in perinatal morbidity and mortality and, in addition, an inclination to certain chronic illnesses such as diabetes mellitus type II, coronary disease, stroke and hypertension in adulthood.3 On the other hand, the increased prevalence of obesity among pregnant women is associated with both obstetric complications such as hypertensive disorders of pregnancy and caesarean sections as well as high-birth weight infants.3

In addition to the effect of weight on the above-mentioned diseases, researchers are currently studying the effect of birthweight on cancer, diseases affecting kidneys, lungs, and the immune system as well as learning ability, mental health and aging.5

Nutrition during Pregnancy: Macronutrients and Micronutrients

There is an increase in the energy requirements during pregnancy as well as an increased need for macronutrients and micronutrients.


Macronutrients such as proteins, fats, carbohydrates and dietary fibre when adequate in diet, ensure a healthy pregnancy.3 Macronutrient intake is important irrespective of dietary preferences.  Studies indicate that vegetarians eat less protein and more carbohydrate.  Some expectant mothers may choose fortified foods to meet their nutritional needs.3

As per the Dietary Reference Intakes (DRIs), there is no extra estimated energy requirement for the first trimester.  During the second and third trimesters, the extra energy needed per day is 340 and 452 Kcals, respectively.  This is inclusive of increased metabolic activity of the maternal and foetal tissues as well as for the growth of the foetus and placenta.  Foetal growth is dependent on energy preferentially derived from carbohydrates.2,6

Energy requirements and recommended weight gain in pregnancy

The energy requirements increase in pregnancy by about 12%, with the highest energy requirements during the late stages of pregnancy.2  This energy intake is monitored by the weight gained during pregnancy.3  The 2009 American Institute of Medicine (IOM) recommendations for weight gain are shown in the table.

IOM recommendations for weight gain during pregnancy3

Weight categoryBMI (kg/m2)Recommended weight gain (kg)
UnderweightBMI < 18.512.5–18.0
Normal weightBMI 18.5–24.911.5–16.0
OverweightBMI 25.0–29.97.0–11.5
ObeseBMI ≥305.0–9.0


During pregnancy, additional protein is required for foetal, placental and maternal tissue development.6 For healthy foetal development, adequate protein intake is essential as the proteins provide the basic building blocks for various muscles, collagen, enzymes and antibodies.1

The protein requirements are increased from 46 g/day for an adult, non-pregnant woman to 71 g/day during pregnancy.  This represents an average change of 0.8 g/kg/day of protein/day for non-pregnant women to 1.1 g/kg/day during pregnancy.6  Protein requirement is higher in women carrying multiple pregnancies.

Carbohydrates and dietary fibre

Carbohydrates are the largest source of energy in a pregnant woman. It provides for approximately 55% to 75% of the energy needs.3 Adequate carbohydrate intake ensures adequate glucose for maternal and foetal brain metabolism.  Foetal metabolism also uses glucose as its primary energy source.2 Low-energy density or low-glycaemic index (GI) food sources such as whole grains and cereals should be chosen to meet the recommended energy requirement from carbohydrates.  These low GI foods cause a slow and sustained increase in the blood sugar as they are digested slowly.  In addition, these provide dietary fibre as well.2 The recommended daily allowance for carbohydrate in a pregnant woman is 175 g/day.1


Fats are concentrated sources of energy.  They act as a vehicle for absorption of fat-soluble vitamins A, D, E and K.1,2  Fats should provide 25% to 30% of total energy need of a pregnant woman.2  Fatty acids are of 3 types:2

  • Saturated
  • Monounsaturated
  • Polyunsaturated

The polyunsaturated fatty acids (PUFAs) are omega-3 and omega-6 fatty acids.2 PUFAs are an integral part of the neural tissue and are essential for the formation of the brain and retina.1,2

These fatty acids are not synthesized by the body and have to be consumed either through diet or supplements.6 The omega-3 fatty acids are metabolised into biologically active forms—eicosapentanoic acid (EPA), docosahexaenoic acid (DHA) and docosapentanoic acid (DPA).2,6  DHA supplementation during the third trimester of pregnancy and the first 2 years of infancy helps with the rapid brain development.6

Revised 2002 DRI recommendations for essential fatty acids is 10 g/day of omega-6 and 1 g of omega-3.2

Dietary fibre

The high levels of progesterone in pregnancy affect the smooth muscle tone of the gastrointestinal tract with decreased rate of transit of food through the gastrointestinal tract and resultant higher absorption of water.  This may lead to constipation.2 Thus adequate intake of dietary fibre allows for proper gut function and regular laxation.  It also reduces risk for many diseases such as cancers and diabetes and heart diseases.2


Supplementation of vitamins and minerals may be required in pregnancy.  These include vitamins such as A, D, B, vitamin B12, folate and minerals such as calcium, iron, magnesium, zinc, and iodine.

Vitamins and minerals in pregnancy1,2,3,6

NameCategoryRole in foetal developmentDietary reference intakes(DRIs)Results of deficiency
 Vitamin ALiposolubleInvolved in gene expression, cell differenciation, development of foetal organs such as heart, ears, limbs, vertebrae and spinal cord and in vision770 μg/dayLinked to night blindness and increased risk of infection due to weakened immune system
Vitamin DLiposolubleInvolved in bone health and skeletal homeostasis as well as for absorption of calcium. It is important for regulation of genes associated with normal implantation and angiogenesis600 IU/day. Supplementation is advised for women with poor exposure to sunlight or those who are strict vegetariansAffects genetic imprinting affecting neurodevelopment, immune function and leading to various chronic diseases susceptibility. It may also result in congenital rickets and fractures in the newborn
Vitamin  BWater solubleIn general the B vitamins act as cofactors in energy metabolism B12
Vitamin B6 (pyridoxine)Acts as a coenzyme in protein, carbohydrate, and lipid metabolism, formation of red blood cells (RBCs), antibodies, neurotransmitters.1.9 mg/dayAffects brain development and cognitive function.
Vitamin B9 (Folate)Role in nucleotide synthesis, and supports rapid cell growth, replication, and cell division400–600 μg/day before conception and the first 12 weeks of gestationImpaired foetal neural development and growth resulting in neural tube defects such as spina bifida and anencephaly
Vitamin B12 (cobalamin)Role in production of normal RBCs and healthy functioning of nervous system2.6 μg/day.Megaloblastic anemia and neural tube defects
Vitamin CWater solubleInvolved in synthesis of collagen and neurotransmitters. Has a role in iron uptake. Has antioxidant properties85 mg/dayPremature rupture of membranes, pre-term delivery, and infection
IronRole in hemoglobin production, neurodevelopment, and is a cofactor for enzymes involved in oxidation-reduction reactions in cell metabolism. Maximum requirement is in the last trimester27 mg/day, mostly based on individual assessmentLow neonatal birth weight, maternal mortality, premature labour, low cognition and lifelong irreversible neurologic effects
CalciumDevelopment and maintenance of foetal skeleton and hormonal adaptations during pregnancy such as those that affect intestinal and renal absorption. Maximum requirement is in the last trimester1000 mg/dayGestational hypertension, preterm delivery, and pre-ecclampsia
IodineIodine helps regulate metabolism and plays an important role within the thyroid in controlling many body processes. Iodine deficiency is the biggest cause of mental retardation worldwide.140 μg/dayToo little iodine in pregnancy is associated with learning disability in infants and children
ZincZinc plays a role in enzyme and insulin production, and is important for the baby’s health and development.Zinc helps to form the baby’s organs, skeleton, nerves and circulatory system.7mg/dayImpaired growth & development


Deficiency of any micronutrient or macronutrient has an impact on the rapid development of the foetus and may lead to specific birth defects.  In the last trimester of pregnancy, the foetus builds its store of nutrients, both macronutrients and micronutrients, for its early development once outside the womb.  Hence a well-balanced nutritious diet plays an important role in maintaining the proper functioning of all the body systems.


  1. Brown LS. Nutrition requirements during pregnancy. In: Sharlin J, Edelstein S, editors. Essentials of life cycle nutrition. Chapter 1. Sudbury, MA: Jones and Bartlett Publishers; 2011. p. 1-24.
  2. Ministry of Health. 2006. Food and Nutrition Guidelines for Healthy Pregnant and Breastfeeding Women: A background paper. Wellington: Ministry of Health.
  3. Plećaš D, Plešinac S, Vučinić OK. Nutrition in Pregnancy: basic principles and recommendations. Srp Arh Celok Lek. 2014;142(1-2):125-30.
  4. Academy of Nutrition and Dietetics. Practice Paper of the Academy of Nutrition and Dietetics: Nutrition and Lifestyle for a Healthy Pregnancy Outcome [Online]. 2014 [cited October 13, 2017]. Available from
  5. Ross MG, Desai M. Developmental origins of adult health and disease. In: Gabbe SG, Niebyl JR, Simpson JL, Landon MB, Galan HL, Jauniaux ERM, et al., editors. Obstetrics: normal and problem pregnancies. 7th ed., Chapter 5. Philadelphia, PA: Elsevier, Inc. p. 83-99.
  6. West EH, Hark L, Catalano PM. Nutrition during pregnancy. In: Gabbe SG, Niebyl JR, Simpson JL, Landon MB, Galan HL, Jauniaux ERM, et al., editors. Obstetrics: normal and problem pregnancies. 7th ed., Chapter 7. Philadelphia, PA: Elsevier, Inc. p. 122-35.
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