The amount of each nutrient should be based on a thorough food log of no less than 5 days long that records the time of consumption of foods and fluids, approximate amounts in ounces and time of day of consumption. The amount of proteins, carbohydrates and fats should always be based on the woman's body weight in killograms related to her total caloric needs (medical charts exist that estimate the total caloric requirements of a pregnant woman). Other health issues might change the food recommendations for proteins, carbohydrates and fats. Foods should be emphasized and nutritional supplements given if needed only; however, a prenatal is a basic and is always recommended. The amount of folic acid, an important B-vitamin, helps to prevent birth defects (80% of BD are from deficiency of folic acid), but this vitamin must be supplement before pregnancy occurs to have this preventative effect.
We measure folic acid levels and a test that tell us if the women has a genetic problem with folic acid called homocysteine and supplement exactly what they need to normalize testing. Iron is given in the miligram dose range unless ever anemia exists and then the dosage is increased based on the woman's hemoglobin, hematocrit and red blood cell count. Dietary intake does not guarantee that nutritional needs will be met. Calcium is given usually at around the 1000-1500 mg range daily, but needs increase during lactation. Vitamin D is only given if found deficient; as important as it is too much (relative to the woman's needs) can be teratogrnic (can cause birth defects just like too much vitamin A). Zinc is only given if blood levels are low or if the woman displays signs of deficiency such as dry skin, hair loss, splitting nails, chronic infections, etc - but other issues can cause these symptoms as well. Overall, additional zinc is not recommended unless absolutely needed; the red blood cell zinc test is the best test not the serum zinc. Vitamin E is not given as it can cause issues such as increasing bleeding time; if the woman has a deficiency it is of course supplemented at a minimum dose of 400 IUs per day. A B-complex is always given as the prenatal, but the levels of B-vitamins in prenatal are too low to be optimally useful and I like to give a better multivitamin that also has reasonable, and not too high (often true of prenatal vitamin).
The overall diet for a pregnant women should be ongoingly monitored for issues such as constipation, heart burn (reflux) diarrhea, back pain, fatigue, nausea, depression, headache and other issues common to pregnancy.