Can I apply for H4 EAD now?

[mkoct]

Hi,

Our current visa expires on 20-May-2017 and have the I-797 approval for this.
we also got our I 140 approval (approved on 05-July-2016)

My spouse's company will be applying for extension based on I 140 approval by Dec-2016.

Should I wait I 797 approval based on I 140 approval to apply for H4 EAD or can I apply for the H4 EAD based on the current I 797.


Your help is appreciated.

Thanks