Urgent : H1B to H4 when Spouse's H1B is in extension

[Abhirup]

My wife and i both are in H1B in USA. My H1B is under extension and not approved yet. My wife cannot continue any more and wants her H1B to be converted to H4. Can she file a I-539, when my own H1B is under extension, and an approval has not arrived yet. 

I checked the USCIS and saw that they do allow it. Furthermore, if she applies for it, then what document do i need to provide instead of an approved I-797, as it is under extension ? Will a receipt of the filed I-129 help in this case ?

Please help me out with this ?

[pontevecchio]

She would be applying based on a pending H1 extension for you. The form instructions are quite clear.