A pregnant woman needs to ensure that her diet provides enough nutrients and energy for her baby to develop and grow properly, and also to make sure that her body is healthy enough to deal with the changes that are occurring.

For a healthy pregnancy, the mother’s diet needs to be balanced and nutritious – this involves the right balance of proteins, carbohydrates and fats, and consuming a wide variety of vegetables and fruits. If you are pregnant and your diet may be impacted by ethical beliefs, religious requirements, or health conditions, you should check with your doctor.

A pregnant woman’s calorie intake grows during pregnancy. However, this does not mean she should eat for two, i.e. her calorie consumption does not double, it just goes up.
Weight gain, if the mother is carrying just one baby, varies considerably. According to the Institute of Medicine, USA, a woman whose body mass index (BMI) is between 18.5 and 24.9 should gain from 25 to 35 pounds (11.4-15.9 kilograms) during the nine months. A woman who is overweight at the start of pregnancy should gain between 15 to 25 pounds (6.8 to 11.4 kg).

Weight gain recommendations may also vary, depending on the woman’s age, fetal development, and her current health.

Excessive or insufficient weight gain can undermine the health of both the fetus and the mother. (Up to the eighth week of pregnancy the baby is called an embryo, after that, when its major structures have formed, it is called a fetus)
What should I eat during pregnancy?
As mentioned above, the mother should follow a varied, balanced, and nutritious diet, and it must include:

Fruit and vegetables
Aim for five portions of fruit and/or veggies per day. They may be in the form of juice, dried, canned, frozen, or fresh.
Fresh and frozen (if frozen soon after picking) produce usually have a higher vitamin and other nutrient content.
Experts stress that eating fruit is usually better for you than just drinking the juice.

Starchy carbohydrate-rich foods
Starchy carbohydrate-rich foods include potatoes, rice, pasta, and bread.

Protein
Good animal-sourced proteins include fish, lean meat and chicken, as well as eggs. Vegan mothers should consider the following foods as good sources of protein: Quinoa (known as a “complete protein”, it is said to have all the essential amino acids), tofu and soy products. Beans, lentils, legumes, nuts, seeds and nut butters are also good sources of protein. (Beans, lentils and legumes are also rich in iron)

Eating seafood reduces anxiety during pregnancy – British and Brazilian researchers reported in the journal PLoS ONE (July 2013 issue) that pregnant women who regularly ate seafood had lower levels of anxiety compared to their counterparts who did not. Pregnant mothers who never consumed seafood had a 53% greater risk of suffering from high levels of anxiety, the authors wrote.

Fats
Fats should not make up more than 30% of a pregnant woman’s daily calories. Researchers from the University of Illinois reported in the Journal of Physiology that a high-fat diet may genetically program the baby for future diabetes.

Examples of foods high in monounsaturated fats include olive oil, peanut oil, sunflower oil, sesame oil, canola oil, avocadoes, and many nuts and seeds.

Fiber
Wholegrain foods, such as whole meal (wholegrain) bread, wild rice, wholegrain pasta, pulses, fruit and vegetables are rich in fiber. Women have a higher risk of developing constipation during pregnancy; eating plenty of fiber is effective in minimizing that risk. Studies have shown that eating plenty of fiber during pregnancy reduces the risk (or severity) of hemorrhoids, which also become more common as the fetus grows. Fiber can also help prevent obesity; something the mother should try to avoid.

Calcium
It is important to have a healthy daily intake of calcium. Dairy foods, such as milk, cheese, milk and yoghurt are rich in calcium. If the mother is vegan, she should consider the following calcium-rich foods, calcium-fortified soy milk and juices, calcium-set tofu, soybeans, bok choy, broccoli, collards, Chinese cabbage, okra, mustard greens, kale, and soynuts.

Zinc
Zinc is a vital trace element. It plays a major role in normal growth and development, cellular integrity and several biological functions, including nucleic acid metabolism and protein synthesis. Since all these functions are involved in growth and cell division, zinc is important for the growth and development of the fetus.

The best sources of zinc are chicken, turkey, ham, shrimps, crab, oysters, meat, fish, dairy products, beans, peanut butter, nuts, sunflower seeds, ginger, onions, bran, wheat germ, rice, pasta, cereals, eggs, lentils, and tofu.

Iron

The following foods are rich sources of iron:

Dried beans, Dried fruits, Egg yolk, Lean meat, Oysters (make sure they are cooked if you are pregnant), Poultry, Salmon, Tuna.
Lamb, pork and shellfish also contain iron, but less than the items listed above
Legumes – lima beans, soybeans, kidney beans, dried beans and peas
Seeds – Brazil nuts and almonds
Vegetables, especially dark green ones – broccoli, spinach, dandelion leaves, asparagus, collards, and kale.
Wholegrains – brown rice, oats, millet, and wheat.
Non-animal sources of iron, even though their iron-content may be high, are less easily absorbed by the human body. Mixing some lean meat, fish or poultry with them can improve their absorption rates by up to threefold.

Some teas, such as commercial black tea or pekoe teas have chemicals that bind to iron and make it much harder for the body to absorb the iron.

Source: http://www.medicalnewstoday.com/articles/246404.php