The election duty may be cancelled if a request along with the medical certificate to this effect is enclosed.

Yes you can apply with the reason and supporting documents to DIstrict collector to cancel your duty. 

Yes you can apply your leave on this exceptional case.

You can make representation to district election officer that wife would be 9 months pregnant at time of elections and henc your election duty may be cancelled . Enclose wife medical certificate about complications in her pregnancy

2) your application for exemption can be granted on humanitarian grounds .if your representation is rejected you would have to do election duty

3) if you refuse to do election duty FIR can be filed against you

Has she already written to her departmental head for this? If yes, then she can file a writ petition in the High Court to seek quashing of the order of election duty.

Your wife is eligible for exemption from duty on this ground and not you. 

You may still go ahead and apply for a leave but I am doubtful that the same will be given to you.

regards

The due date is very close and hence this reason alone is sufficient for the government to cancel the election duty.

Regards 

Dear Sir,

You may representation before higher authorities along with medical records, if no action taken then approach Service Tribunal or High Court it will stay immediately such deputation order.

Dear Client,

Election duty can be cancel by same officer who assigned you. Pregnancy of wife may not the perfect reason to deny duty unless medical condition to deliver a child is threaten, still you can sight this reason. 

You can submit an application to this effect along with the proofs for seeking exemption from this duty.

Your request, if found to be genuine, may be accepted