Women who started at a normal weight before pregnancy need an average of 300 extra calories per day during their second and third trimesters.  Normal-weight women should consume between 1900 and 2500 calories daily. Eating more calories than recommended may lead to an unhealthy increase in weight. If you were underweight, overweight, or obese before pregnancy, discuss your caloric needs with your doctor. These needs vary from person to person. Even if there are rare circumstances surrounding your pregnancy that make weight loss a healthy option, you may still need to maintain or increase your caloric intake. You should also talk to your doctor about your caloric needs if you are pregnant with multiples. You will likely need even more calories if you are carrying more than one baby. Empty calories will lead to unnecessary weight gain but will not provide your baby with any of the nutrients he or she needs. Avoiding empty calories is vital in maintaining a pregnancy weight that is healthy for you.  Avoid foods with added sugars and solid fats. The usual culprits include soft drinks, desserts, fried foods, rich dairy products like cheese or whole milk, and fatty cuts of meat. Opt for low-fat, fat-free, unsweetened, and no-added sugar options when available. Also avoid caffeine, alcohol, raw seafood, and potential sources of bacteria. Your body will have additional nutritional needs during pregnancy. Prenatal vitamins allow you to address these needs without having to ingest more calories than absolutely necessary.  Never rely on prenatal vitamins as a substitute for actual food, even if your doctor tells you that weight loss is acceptable for your circumstances. Supplements are absorbed best when taken with food, and vitamins obtained from food are generally easier for your body to access than those obtained through supplements. Folic acid is one of the most important prenatal vitamins you can take. It markedly minimizes the risk of neural tube defects. Iron, calcium, and omega-3 fatty acid supplements also help...

===
Write a summary of the previous text in Vietnamese:
Nắm được nhu cầu calo. Tránh ăn những món ăn chứa năng lượng rỗng và không lành mạnh. Uống vitamin dành cho bà bầu. Ăn những bữa ăn nhỏ và thường xuyên. Duy trì một bữa ăn lành mạnh giàu dinh dưỡng phù hợp với bà bầu. Ăn nhẹ lành mạnh. Tập thể dục nhẹ nhàng.