Get enough protein! Consider the percentage protein in the food you choose. With food labels, a simple way of doing this is to compare the quantity of protein in grams to the energy content in calories. This is not a scientific comparison but is a rule-of-thumb when shopping. The closer the ratio of the protein grams to calories is to 1:10, the better the nutrition, for example 22 grams protein vs 220 calories.
Protein. Have a protein source with every meal to help keep blood sugars stable. Avoid too much sugar and simple carbohydrates and eat complex carbs and whole grains, and don't forget the veggies. You need an extra 100-300 calories during pregnancy, so don't eat for two! a normal weight woman should only gain 25-35 lbs. Goal weight gain is less if you are overweight and more if you are underweight.
High-quality protein. The quality of the protein you eat is another important matter. Proteins from meat, eggs, fish, poultry are very good and from milk-based foods such as cheeses are fairly good, but the quality drops off rapidly with soy-based meat substitutes and very rapidly with most vegetables, so discretion is needed.