During pregnancy the body is going though many changes and as result nutrition is of most importance during this time. As an example, in Canada there are specific programs (e.g., The Canada Prenatal Nutrition Program (CPNP)) that are targeted to vulnerable pregnant women which typically provide food supplements and individualized counselling. The CPNP aims to reduce the incidence of unhealthy birth weights, improve the health of both infant and mother and encourage breastfeeding. The general consequences of malnutrition during pregnancy include:

• Fetal growth retardation
• Congenital malformations
• Miscarriage and stillbirth
• Premature birth
• Low infant birthweight

Malnutrition and low birth weight contribute to over 50% of deaths of children under the age of 5 worldwide. To support the changes in pregnancy and the growth of the baby, more nutrients and calories are needed. In addition, there are a variety of other nutrition-related concerns that can occur during pregnancy and can be effectively managed. These are discussed in further detail.

First, we begin with an overview of pregnancy

Placental Development

The placenta develops in the early stages of pregnancy. The amniotic sac and umbilical cord also develop in the early stages. These three structures play critical roles during pregnancy and are expelled from the uterus after childbirth. The placenta is a spongy tissue in which fetal and maternal blood each flow side by side, each in its own blood vessels. Maternal blood transfers oxygen and nutrients to the fetus’ blood and picks up fetal waste products. The placenta plays the roles of the lungs, kidney and digestive system for the fetus. It is a metabolically active organ that requires energy and nutrients. The placenta also produces hormones that maintain the pregnancy and prepare the mother’s breasts for lactation.

Fetal Growth and Development
Fetal development begins with the fertilization of the egg (ovum) and goes through three stages:

1. Zygote
The fetus begins as a single cell and becomes multi-cellular. Within 2 weeks the zygote embeds itself in the uterine wall in a process called implantation. As development proceeds, the zygote becomes an embryo.

2. Embryo
At first, the number of cells in the embryo double every 24 hours then the rate slows down. At 8 weeks, the embryo is 30 mm in length and has a complete central nervous system, a beating heart, a digestive system, well defined fingers and toes and the beginnings of facial features.

3. Fetus
The fetus is a developing infant from 8 weeks on and is full term at 38 weeks. Fetal growth is amazing – going from < 1 g to 3500 g (7.5 pounds- on average) during that time. Critical Periods are times of intense development and rapid cell division. They are critical in that an event can only occur then. If adversely influenced at this point, development is permanently impaired. Each organ and tissue is most vulnerable to adverse effects during its own critical period. For example, the neural tube forms the beginning of the brain and spinal cord. Its critical period is from 17 - 30 days of gestation. During this time neural tube development is most vulnerable to nutrient deficiencies or toxins. At this point, many women do not know that they are pregnant and abnormal development of the neural tube or failure of it to close completely can cause a major defect in the central nervous system. This is referred to as a neural tube defect. The most common neural tube defects are anecephaly (a fatal condition characterised as a partial absence of brain tissue) and spina bifida (incomplete closure of the spinal cord). With spina bifida (latin for 'open spine'), there are varying degrees of paralysis, depending on the extent of the spinal cord damage. Common problems of spina bifida include club-foot, dislocated hip, kidney problems, muscle weakness, impaired mental abilities, motor and sensory losses. Mild cases may not even be noticed but severe cases can result in death. The addition of folic acid to the diet of women of child-bearing age (approximately 14 to 45 years) may significantly reduce, although not eliminate, the incidence of neural tube defects. It is estimated, however, that 70% of all NTDs could be prevented simply by consuming enough folate. As previously indicated in the preconception nutrition notes, it is recommended that all women of child-bearing age consume 0.4 mg of folic acid daily, especially those attempting to conceive or who may possibly conceive. It is not advisable to wait until pregnancy has begun, since by the time a woman knows she is pregnant, the critical time for the formation of a NTD has usually already passed. Grain products are fortified with folate and adequate folate intake is estimated to reduce NTD by 50%. There is however, the risk of masking B12 deficiency. NUTRITION-RELATED CONCERNS The nutrition issues in pregnancy related to weight status, macronutrient needs, micronutrient and fluid needs and common conditions that arise in pregnancy that can affect nutrition. These are discussed in further detail. 1. Energy Needs and Weight Status

Birthweight is the most reliable indicator of an infant’s health. Generally, higher birth weights indicate less health risk for infants. The mother’s pre-pregnancy weight and weight gain during pregnancy may affect birthweight of the infant.

Underweight Women

Underweight women (BMI < 18.5) tend to have smaller babies than heavier women. A woman who is underweight prior to pregnancy is at risk for a low birthweight baby (<3500 grams) particularly if she is not able to gain adequate weight during pregnancy. The rates of preterm births and infant mortality are higher and extra weight gain during pregnancy (recommended range of weight gain is 12.7 to 18.2 kg or 28 to 48 lbs) is recommended. Overweight or Obese Women

Overweight (BMI 25.1 to 29.9) or obese (BMI => 30) women have an increased risk of complications during pregnancy and childbirth such as hypertension and gestational diabetes. Overweight women tend to have more induced labor and C-sections. Infants are more likely to be born post term and weigh more than 4 kg (9 pounds). Weight loss diets are not advisable during pregnancy as good nutrition is important as well as some weight gain (recommended range of 6.8 to 11.4 kg or 15 to 25 lbs). It is recommended that, women reach a healthy weight prior to becoming pregnant and avoid excess weight gain during pregnancy.

Healthy Weight

The ideal pre-pregnancy weight range should fall within a BMI of 18.5 to 25. Weight gain during pregnancy is necessary, and a gain of 11.5 – 14 kg (25 – 30 pounds) is recommended. If the mother is expecting twins weight gain should range between 16 to 20 kg (35 to 40 lbs).

This distribution of weight gain is outlined in Table 1.

The norm is to gain 1-2 kg (2-4 pounds) in the first trimester and 0.5 kg (1 pound) per week thereafter.

Table 1: Weight Gain in Pregnancy
Blood 2 kg
Breasts 1.5 kg
Placenta 0.5 kg
Amniotic Fluid 1 kg
Baby 4.5 to 5.5 kg
Extra fat stores 2.5 to 3.5 kg

Most women generally lose the weight after pregnancy. Although, some women may still look pregnant, there is some weight loss immediately at delivery. There continues to be a loss of blood volume and fluids over several weeks. Most women tend to return to a weight slightly above their prepregnancy weights.

2. Macronutrient Needs in Pregnancy

During the 1ST trimester the body requires an extra 100 kcal/day. During the 2nd and 3rd trimesters this increases to an extra 300 kcal/day. Nutrient needs expand more than energy needs so the mother needs nutrient dense foods. Protein needs increase of 5 g, 20 g, 25 g per day in each trimester is needed. Protein needs are easily met. Carbohydrate intake should be at least 130 g per day to prevent ketosis. Requirements for fat do not change; however, it is important to note that the essential fatty acids are a key nutrient required in pregnancy.

Docosahexaenoic (DHA), an omega 3 fatty acid is critical to brain and eye development. Good sources are coldwater fish and it is generally recommended that pregnant women can safely consume 340 g (12 ounces) of fish per week to avoid mercury contamination. Large fish like swordfish, shark, fresh or frozen tuna, and marlin as well as canned tuna from the large “Albacore” or “Bluefin” species (often labelled as “White”) should be avoided in pregnancy.

3. Micronutrient and Fluid Needs in Pregnancy

The key nutrients during pregnancy include folate/folic acid, vitamin B-12, vitamin C, vitamin A, vitamin D, calcium, iron, zinc, and iodine.
Folate and vitamin B12 are needed for cell division. The recommended intake for folate, more than doubles in pregnancy (RDA is 600 mcg/day). Dietary sources should be emphasized although supplements are usually recommended. There is a slight increase in B12 needs. In diets that contain animal products, it is not a problem to obtain adequate amounts.

Insufficient intake of vitamin D and calcium may result in abnormal fetal bone development. Adequate vitamin D is usually obtained from milk and sunlight. Vegetarians who do not eat milk, eggs and fish must get vitamin D from the sun or fortified soy milk as there is an increased risk of toxicity with supplements. The RDA for vitamin D during pregnancy is 5 mcg/day. Calcium absorption, more than doubles during pregnancy. Fetal bones begin to calcify in the last trimester. In the final weeks of pregnancy more than 300 mg of calcium is transferred each day. Calcium needs are met with an adequate intake of milk and dairy and other calcium rich foods or supplements. The DRI for calcium during pregnancy is 1300 mg/day for women <18 and 1000 mg/ay for women 19-50 years. More iron is needed to support the increased maternal blood volume and for placental and fetal needs. There are changes that help meet iron needs. Periods stop, iron absorption increases (3 times) and transferrin levels increase. Anemia often occurs at the beginning of the second trimester and can mask as simply "pregnancy fatigue." It is common for physicians to test hemoglobin status at this point in the pregnancy. The fetus draws on maternal iron stores to lay its own stores for the first 6 months as milk is the only food and it is low in iron. Women tend to have low iron stores so iron supplements are recommended. Hemoglobin should be tested at the beginning of the pregnancy to determine iron stores. Zinc is required for DNA and RNA synthesis and a low zinc status leads to low birthweight. Zinc supplements are not generally recommended. Vitamin A needs in pregnancy increase from 700 to 770 mcg/day. Women taking a prenatal supplement should be advised not to take more than 10,000 IU per day of Vitamin A. This could increase the risk of birth defects. Provitamin A (beta-carotene converted to vitamin A in the body) has not been associated with birth defects. Vitamin C requirements increase by 10 mg/day in pregnancy in order to produce collagen.Lastly, iodine needs increase from 150 mcg to 220 mcg/day and is easily achieved through the diet. The AI for total fluid intake is 3 L per day of nondiuretic fluid (e.g., water, soups, juices, milk and sport beverages). This helps to prevent fluid retention, constipation and urinary tract infections. Nutritional SupplementsMost women take a daily prenatal multivitamin and mineral supplement (e.g. 'Materna' contains 1 mg folate and 30 mg iron). The needs for most nutrients except for iron are easily met with a varied diet. 4. Other Common Nutrition-Related Concerns During Pregnancy

There are some common discomforts and disorders of pregnancy women that are related to their general nutrition.

Nausea and Vomiting

Nausea can be mild to severe and is referred to as ‘morning sickness’. Women with severe nausea and vomiting (hyperemesis gravidarum) are at risk for dehydration, electrolyte imbalances, abnormal metabolism and weight loss. Fifty to eighty percent of pregnant women experience nausea and vomiting; about one percent suffer severe symptoms. It seems to be relate to hormonal changes. The best way to counteract nausea is to eat dry crackers, ginger, have small, frequent meals and avoid offensive odours.

Constipation and Hemorrhoids

Constipation affects 11 to 38 % of pregnant women. Dietary and lifestyle changes usually correct it.Constipation during pregnancy is linked to several physiological changes associated with pregnancy and an eating pattern low in fibre and liquids. The hormones of pregnancy alter muscle tone and absorption of water from the colon, the growing fetus pushes on internal organs. Ways to overcome these problems are to increase fiber intake, drink plenty of water, exercise and use the bathroom frequently. Decreased physical activity, extra bed rest and iron supplements may also contribute to this common discomfort.Increase fibre intake by eating more whole grain breads and cereals; vegetables; and fruit and legumes such as beans, split peas and lentils as well as drinking between 8 and 12 cups of fluid every day in the form of water, milk and juice may help. Maintaining an active lifestyle, for example, by walking or swimming regularly can also prevent this problem.

Heartburn

Heartburn is caused by gastric reflux. Reflux is more likely to happen during pregnancy because the enlarging uterus presses on the stomach and can force stomach contents up into the esophagus. To prevent heartburn consuming small, frequent meals, avoiding spicy and greasy foods, sitting up while eating, sleeping with the head of the elevated, and waiting an hour after eating before lying down are general suggestions that are provided.

Food Cravings and Aversions

These are likely related to hormone-induced changes in sensitivity to taste and smell. Pica, the craving for non-founds such as clay can be a concern.

Preexisting Diabetes

It is best to get diabetes under control before becoming pregnant. Poor control can also result in decreased fertility. Being hypo- or hyperglycemic, or having hypertension can result in miscarriage.

Gestational Diabetes

Approximately 1 in 25 women develop gestational diabetes. Gestational diabetes occurs typcially during the second half of pregnancy. It is standard procedure to for pregnant women to have a glucose tolerance screen between 24-28 weeks of gestation. If gestational diabetes is diagnosed, it is treated with a combination of diet, exercise and usually insulin. The most common consequences of gestational diabetes are high birth weight and complications during labour and delivery. After childbirth, the mom’s glucose levels return to normal. However, women who had gestational diabetes are at risk for developing type 2 diabetes later in life.

Hypertension

It is best to bring hypertension under control with diet, weight loss or medication, prior to becoming pregnant. During pregnancy transient hypertension can occur. For most women this is very mild and of no concern. If severe, it results in a low birth weight baby or stillbirths (the placenta becomes detached). Pregnancy Induced Hypertension (Pre-eclampsia) is a complication of pregnancy characterized by high blood pressure, protein in the urine and edema. Pre-eclampsia is associated with genetics and deficiencies in vitamin C, vitamin E and magnesium. It usually occurs after 20 weeks, most often near term and results in reduced blood flow to the baby. The placenta can detach resulting in a stillbirth. It can progress to eclampsia resulting in coma and convulsions. This condition needs prompt medical attention.

Pregnancy in Adolescence

Young women have high nutrient needs for growth and development. They are still growing themselves, laying down bone, so their calcium needs are high. The needs of the baby are over and above these. The recommended weight gain for teenage mothers is higher than for older women. Young mothers have unique physical, economic and psychosocial concerns and may be at greater nutritional risk as most have limited finances. They are experiencing many situations such as school, peer pressure, poor self confidence and fear if they are single. Prenatal care is important. There are programs in Canada available for high risk pregnancies such as ‘Healthiest Babies Possible’.

Lifestyle Factors and Pregnancy

Drugs (including alcohol), whether medical or illicit as well as smoking/chewing tobacco can affect oxygen and nutrient delivery as well as waste removal. This can lead to increased pre-term, low birth weight and infants more prone to SIDS. Children may have abnormal behaviour and poor cognitive development. Alcohol intake during pregnancy can result in birth outcomes of fetal alcohol effects and fetal alcohol syndrome (discussed later).

Environmental contaminants such as lead and mercury as well as vitamin and mineral megadoses can have toxic effects. Caffeine has not been linked specifically to birth defects but it is recommend to limit intake to 300 mg/day from all sources. This is 100 mg/day less than the limit for the average adult. Caffeine is consumed as a natural part of coffee, tea, chocolate and certain flavours (e.g. those derived from kola and guarana), and may be added to cola-type beverages. Caffeine exhibits a number of biological effects resulting from its diuretic and stimulant properties. Currently, pure caffeine may be added to cola-type beverages and it must be declared in the ingredients list on the product label. Caffeine may not be added to any other food. Many foods and food ingredients contain caffeine from natural sources. The caffeine in food from natural food ingredients, crude extracts or natural flavours is not regulated when such ingredients are added to food. Other products, such as guarana, a Brazilian plant whose seeds are high in caffeine, and yerba mate, a South American herb used to make tea, are also natural sources of caffeine. These are increasing in popularity, and are being used more and more as food ingredients. Energy drinks and beer-like products containing guarana have recently appeared in the Canadian marketplace.

Vegetarianism in general is of no concern in pregnancy. However women who are vegans need to carefully select their foods to ensure adequate vitamin D, vitamin B-6, vitamin B-12, calcium, iron, and zinc. Supplementation with calcium beyond the standard prenatal vitamin/mineral supplement may be needed.
Weight loss dieting is not recommended during pregnancy as it may deprive the fetal brain of glucose. Weight gain is needed.

The use of artificial sweeteners and sugar substitutes in moderation during pregnancy have not been associated with adverse birth outcomes.

Some herbal teas can be harmful in pregnancy. The following are herbal teas generally considered safe if taken in moderation (no more than 2 cups/day): citrus peel, ginger, lemon balm, linden flower, orange peel and rose hip.

Exercise during pregnancy is beneficial and generally recommended.