Not only folic acid but a pregnant woman is required to concentrate on having balanced diet. Avocados are a source of folic acid, vitamin C, B6 and potassium. Try to spread avocados on your whole grain instead of mayo for getting the nutritional benefit. They are high in fat so only take them excessively when there is an issue of weight gain during pregnancy. There are certain food to avoid during pregnancy like undercooked meat or raw meat, unpasteurized milk, and fish with high mercury. It is better to seek advice from your health care provider.