A lot of the women shun the habit of taking alcohol, caffeine nicotine etc. during the period of the pregnancy as it can be harmful for the bay in the womb. So they develop the habit of taking herbal tea to compensate their craving to make them normal for the routine life. 
But as we know that the excess of everything is bad so, it must be kept in mind that the herbal tea is not all safe as many ingredients in the herbal tea can lead to some complications for the process of the pregnancy. Because there have not been considerable research done on the herbs used in the teas.
According to FDA most there are no any allegations on the use of the herbs for the purpose of the food as most of the herbs don’t seem to have any severe kind of the adverse effects on the body. Most of the herbal tea made from the thyme, ginger, lemon, jasmine etc are considered safe if take in small amount like in pregnancy tea 2-3 times. But the usage must not be more than a normal level, as it can cause abnormalities in case of pregnancy and the lactation. So the mothers must understand this fact and avoid the excess usage.
A lot of herbs have been proved of no safe use for the women who are pregnant and they can result in the death of their child in the womb which is not a good thing. Herbal teas made of ingredients like anise, Chamomile, hibiscus, ephedra, lemon grass, mug wort, rosemary, sassafras etc can be really harmful as they can cause the miscarriage. Many people use these herbs in their regular foods. In this matter it is quite safe as it is according to the standards.
Although herbs are prohibited yet they may have some beneficial effects during the pregnancy some of the examples are as following, peppermint herb can be useful source for relieving nausea and vomiting in the women who are pregnant. Lemon balm can alleviate the symptom of the insomnia.
Ginger root is also helpful during nausea and vomiting. Rose hips can result in the increase in the immunity of the people; this can be really helpful in the regular quantities during the period of the pregnancy. Alfalfa is a rich source of the various types of the vitamins so pregnancy tea 2-3 time of alfalfa can be really useful during the stages of the pregnancy.
Dandelion can also be helpful in many regards during the pregnancy. So are the many other herbs available in the nature. But they must be used with the proper advice of the doctor. In the case of any complication one must consult the doctor as it can be helpful to avoid the harmful effects.
There is a proper database for the natural herbs and the medicines one must consult it before the usage of the herbs for the health of the baby and the mother in a proper way.