Weight Gain
This is obviously not the time to try and lose weight. Even if your pre-pregnancy weight was high, there must still be a weight gain to ensure adequate energy for fetal growth and development.

It is estimated that the energy needs for pregnancy are close to 69,000 calories. This translates into an increased caloric intake of 150-300 calories a day. The best method to determine if caloric intake is adequate is to simply measure rate of weight gain (see table 1). Inadequate weight gain is associated with lower birth weight.

Nutrient Needs
In a perfect world, everyone gets the vitamins and minerals that they need from a varied, healthy diet. Of course reality in no way reflects this idyllic view.

Intake studies of pregnant women in the United States show them to be low in B6, D, E, folate, which is vital for proper neural tube development of the fetus, calcium, iron, and zinc.

Female athletes present the same insufficiencies along with B12. Additionally, many female athletes fail to eat sufficient calories and may be underweight prior to becoming pregnant.

For these reasons, almost 90% of pregnant women in the United States use a prenatal vitamin and mineral formula. Potential benefits of supplementation include reduced risk of selected birth defects, improved immune systems and obviously, improved nutrient intake status.

However, with increased energy requirements and food intake, the expectant mother should be able to get a greater degree of these nutrients from food. B vitamin requirements in particular are related to energy needs and intake.

Grains are fortified with thiamine, niacin, riboflavin, iron, and as of a few years ago, folate. Unfortunately, due to the current popularity of low carbohydrate diets, women may not be getting enough of these foods to provide the nutrient levels desired.

Protein requirements are also increased during pregnancy, to the tune of around 10 grams. This is seldom an issue as most American women consume more than enough protein prior to pregnancy. If a woman needs to increase her protein, animal sources may likely be the best bet, since additional vitamins and minerals that are desired during pregnancy can be obtained, such as iron found in meats and calcium found in dairy.

Miscellaneous
Caffeine, alcohol, dietary supplements and performance enhancing supplements should probably be discontinued or severely restricted. There is some evidence that caffeine may be related to lower infant birth weight, while other studies show no effect.

Research has shown alcohol has many adverse effects associated with its use during pregnancy, with the most severe being fetal alcohol syndrome, characterized by varying degrees of physical, emotional and developmental problems.

As for additional dietary supplements and herbs, there is simply no data on their effects on pregnancy and the developing fetus. When in doubt ask your doctor, pharmacist, or other health care professional.