There are no specific juices that are necessary during pregnancy. All fruit and vegetable juices are beneficial for your health, and you should simply make sure that your intake of these juices is varied. As long as you don't consume an excess of any particular juice or juices, you do not need to worry about any juice being harmful. This is true especially if you are drinking fresh juice without any additives including sugar - packaged juices often have added preservatives and other substances that it may not be advisable to consume during pregnancy, but is not the case with fresh juices.
Regarding avoiding an excess - you should take into account the fact that your body will naturally have certain cravings during your pregnancy, and it is usually okay to indulge these cravings unless the indulgence makes you feel physically uneasy. These cravings are usually your body's way of telling you that you and your baby need more of certain nutrients. For example, some pregnant women develop a craving for orange juice and can have several glasses a day without any ill effects - this often seems to be because they have developed a mild deficiency of vitamin C.
Finally, it is always a good idea to get your doctor's opinion, as he or she is more aware of your requirements and the state of your health.
answered by M W