see INS memo

http://www.shusterman.com/hlmemo500.html

Think about it--a H1 who uses EAD to obtain other employment will loose his/her H1 status; but an H4 who can't otherwise work won't loose her status when she uses her EAD? Does it make sense? The question itself implies that H4 using EAD will violate the status, which was specified in earlier documents.

If you want to be safe, wait at least till the 140 is approved before using EAD, otherwise, take the risk at your own peril.
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2. If an H-1 or L-1 nonimmigrant or H-4 or L-2 dependent family member obtains an EAD based on their application for adjustment of status but does not use it to obtain employment, is the alien still maintaining his/her nonimmigrant status?

Yes. The fact that an H or L nonimmigrant is granted an EAD does not cause the alien to violate his/her nonimmigrant status. There may be legitimate reasons for an H or L nonimmigrant to apply for an EAD on the basis of a pending application for adjustment of status. However, an H-I or L-1 nonimmigrant will violate his/her nonimmigrant status if s/he uses the EAD to leave the employer listed on the approved 1-129 petition and engage in employment for a separate employer.