Is Windows Defender needed if using Malwarebytes Pro?

What Anti-virus are you running?

as long as you have an antivirus program running and malwarebytes pro, WD can be shut off.

I use Microsoft Security Essential and Malwarebytes Anti Malware Pro at the same time and they play will together.
When installing Microsoft Security Essential (Anti Virus) it should turn off Defender in Windows 7.
To verify Defender is turned off after installing Microsoft Security Essential go to Start and type in Defender and tick on Windows Defender and it should indicate that Windows Defender is off.

AVG does not like, or play well with Malwarebytes' Anti-malware. Just be aware of that.

If you're running Nod 32 along side of malwarbtyes pro then no there's no need for windows defender to be enabled and can be safely disabled or you can just set it to manual in services instead of disabled to just keep it from starting up at start up.