Beware of gaining too much/not gaining enough weight!
Gaining too much weight during a pregnancy will make you susceptible to pregnancy induced hypertension. However, recent trends have been seeing mothers-to-be that are too slim. It is said that not gaining enough weight will result in not only a smaller infant but also makes you susceptible to lifestyle related diseases. In any case, weight control during gestation is very important.
How much weight gain is normal during pregnancy?
The weight a pregnant woman gains until birth mostly consists of the weight of the infant (fetus), placenta, amniotic fluid and blood. A newborn's average weight is approximately 3 kilograms. It is said that a mother-to-be's body stores up necessary nutrients for birth and breastfeeding during pregnancy as well. In recent time, weight gain calculated according to each individual's pre-pregnancy weight seems to be the most ideal.

DIET & NUTRITION
Diet & Nutrition While You Are Pregnant
During pregnancy, a mother needs to ensure ample nutrition intake to provide for both herself and the baby. Thus, maintaining good prenatal health with a well-balanced diet and adequate nutrient intake is essential for baby to thrive.
Be sure to eat three balanced meals every day while actively incorporating dishes with plenty of protein and iron into your menu.

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Folic Acid
Supplementing 400µg of folic acid daily from one month before pregnancy to third month of pregnancy reduces the risk of neural tube closure in babies. This nutrient can be found in spinach and beans.
Note: Be careful not to exceed 1000 µg a day.
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Calcium
Creates strong teeth and bones. It is found in foods such as milk, dairy products, small fish and soy beans.
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Protein
This nutrient is very important in forming the baby's body. Make sure to have a balanced diet with meat/fish/beans.
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Magnesium
Supports the metabolism of calcium and corrects blood circulation. It can be found in foods such as almonds, green and yellow vegetables and bananas.
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Iron
Iron creates red blood cells and is essential for preventing anemia. It is found in foods such as liver, eggs, oysters and freshwater clams.
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Dietary Fiber
Dietary Fiber is helpful in preventing constipation in pregnant woman. It is found in foods such as kelp, almonds, konjak, mushrooms and potatoes.
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Avoid salt as much as possible
Unlike the six nutrients mentioned that pregnant women should be actively getting, salt is an ingredient that should be avoided as much as possible. Salt cause swelling and high blood pressure, and is known to lead to pregnancy-induced hypertension (pregnancy toxicosis) as well. Avoid non-homemade soup for noodles, processed foods and pickled foods. Also try to keep your salt intake under 7.5g a day.

Dietary Guideline For Expectant Mothers (Japanese Ministry of Health, Labour and Welfare)