i posted some info (off the ivillage.com website) regarding taking valium during pregnancy BELOW (the women below had her drink spiked with it while pregnant)...it's most likely best NOT to take it, but it seems like a one time (2mg) dose does not pose a risk to the baby. however, really everything we do or don't do may be a risk to the fetus and so you must just weigh your options.
You probably shouldn't take it for your migraines, because if they are reoccurring then a one time dose of valium really won't help you and multiple doses to ease the migraines would be harmful to the baby and potentially addictive. Also, when doing a search on the internet refer to valium as a "benzodiazepines," since that's the technical medical classification for valium--so type a search such as "effects of benzodiazepines on fetus." Valium is the brand name.
Here is the info I found on ivillage.com regarding valium during pregnancy. It seems the neuro prescribed it without concern since it was a small dosage.
Valium
I am 22 weeks pregnant. I was out with a few friends at a housewarming party when a man I didn't know well thought it would be funny to slip about 25 mg. of Valium in my soda. I started feeling funny and then I found out what he had done. He said that he didn't know I was pregnant. What harm can this do to my baby?
I will put aside my natural outrage at such an act long enough to try to relieve your mind. This is a criminal offense, however, and I hope you take action against this person. I know that you will also report this to your own care provider and seek their opinion.
Valium is an anti-anxiety, anti-convulsant medication and generally induces sleepiness. It is a FDA "Category D" drug, which means that "there is positive evidence of human fetal risk." However, the risk is dosage related and a one- time dose is unlikely to produce ill effects on the baby. The typical dose of this drug when given orally is two to ten mg. two to four times a day. You were given a large amount all at once.
Valium is still given in late pregnancy to stop a seizure in a pregnant mother. Most of the adverse effects seen in the newborn relate to an altered state of consciousness -- sleepiness.
I would try not to worry as the effects of one dose would appear to be minimal, but I can understand your concern.
GOOD LUCK!