My doc. put me on terbutaline to stop my preterm labor contractions and when i went online to do some research on it.. i found that it isn't approved by the FDA for that purpose. Obviously there is a reason for why. Which is what i need to know...

Also isn't a doctor required to inform their patients on medication they are giving them or at least tell them their perscribing one that isn't approved by the FDA?

Numerous drugs that are used in relation to pregnancy are not approved by the FDA for that purpose -- the reason being that drug studies, particularly of the size that would likely be required, are not typically conducted on pregnant women. The bottom line is that there is little "hard" data. That is why, for example, if you look up various OTC drugs to see what is okay during pregnant, that vast majority of drugs are not specifically classified to be okay for use during pregnancy...and if you read the descriptions of each classification you'll see that they simply haven't been studied on that population.

So, many of the drugs that are used in relation to pregnancy are drugs that were developed and approved for other uses, and later determined to be helpful with a particular situation -- such as inducing or halting labor. This persists in other areas of pregnancy related meds and, of course, outside the pregnancy arena altogether. For example, metformin (aka glucophage) is a medication used to control blood sugar and insulin, and is used in the treatment of diabetes....and eventually came to be used for the treatment of PCOS (polycystic ovarian syndrome) in women with PCOS generally....and, subsequently, to be used specifically for treating women with PCOS who are trying to conceive. That's not what it's "approved" for but that's what it's used for, and that is normal in the medical world.