Most dietary guidelines are very generic, but the Higgins Intervention Method has specific plans for meeting the special requirements of mothers with different nutritional needs. I like the ability this method gives to really personalize the recommendations and the ability it gives me to quantify the nutritional needs rather than just saying “eat more”.
If you are working with a pregnant teen, she needs more than the standard prenatal calories and protein. This is because her body is still growing, and she needs to eat enough to support both her growth and the growth of her baby. So you would need to add the 300 additional calories a day to the higher values of protein and calories of a teen.
Mothers who are underweight will need to eat an increased protein and calorie diet. However, the Higgins Intervention Method recommends increasing it only for the number of weeks needed to add the weight to make up for the deficit. So if she were 10 pounds underweight, adjust her diet so she gains an extra 1 pound per week for 10 weeks (or 1/2 a pound a week for 20 weeks).
Mothers who are undernourished are determined by the protein intake on the Higgins Intervention Method. To calculate the protein deficit, you would compare her protein intake to the normal pregnancy requirements. To correct for this add as additional daily protein the amount she is deficient and increase her caloric intake 10 calories for each gram of protein she is deficient.
Vegetarian women do not need any different guidelines. They will simply choose animal sources for their food. The biggest struggle, which may not be a struggle at all, will be getting enough protein since vegetable sources of protein are not as protein dense as animal sources. If she has trouble consuming enough calories to get adequate protein she can consider supplementing with any number of a variety of protein supplements.
Lactating women need even more calories than pregnant women. The 300 calorie increase becomes 500 calories. All the principles of good nutrition still apply.