Liverpool will host FA Cup finalists Notts County in the other semi-final, with the dates for both ties in October still to be confirmed.
Three-time winners Arsenal's quarter-final with City was postponed after City were charged with fielding an ineligible player in the group stage.
The charge was found to be unproven and the tie is still to be re-arranged.
Two-time finalists Birmingham knocked out Women's Super League One leaders Chelsea in the last eight.
Liverpool thrashed Bristol Academy in the quarter-finals, while Notts saw off WSL 2 side Reading.
The final of the cup, now in its fifth year, will be held at Rotherham's New York Stadium on Sunday, 1 November.
The full semi-final draw is as follows:
Liverpool Ladies v Notts County Ladies
Arsenal Ladies or Manchester City Women v Birmingham City Ladies

Police Scotland named the men as Craig Munro, 30, and 26-year-old Allan Robertson.
One image appears to have been taken at the same location where missing mother Farrah Fadli was sighted earlier this month.
Police Scotland and the Crown Office said they were unable to confirm if the investigations were linked.
A spokesman for the Crown Office said it was also unable to say, for legal reasons, why the two men were being sought.
Ms Fadli, who is also known as Farrah Gillespie, has been missing from her home in Ayr since Wednesday 12 October.
The 29-year-old initially disappeared with her children but dropped them off at a friend's house in Irvine on 14 October. She has not been seen since.
Ms Fadli is 5ft 4in, of slim build with dyed blonde hair.
She has not gone missing before and officers have said previously it is extremely unusual for her to leave her children for such a long time and not be in touch with her family and friends.
Holders Manchester City or Arsenal will host Birmingham City in the semi-finals of this year's Women's Continental Cup.
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Police have released CCTV images of two men they are trying to trace and have warned the public not to approach them.