1. DNA test can not be sought on assumption only. If you have not established any physical relationship with your wife, then you can seek Court order for DNA test. Her 

2. Her staying with you for 87 days is enough to get impregnated by you. So, if you have established physical relationship with her, then it is no point seeking Court order for DNA test.

3. If she is employed and earns more than 1/3rd of what you earn, then you might escape the liability of paying maintenance to her. However, you shall have to pay maintenance for your child, after she is born.

1. Did you establish physical relationship with her when she stayed with you?

2. If yes, then you can not escape your liability to maintain your child after he/she is born.

If you are of the view that it is not your child and wife had extra marital affair you can gather evidence of her adultery and file for divorce on grounds of mental cruelty and adultery 

2) make her lover co respondent 

3) make application to court for DNA test of the child 

4) wife guilty of adultery is not entitled to any alimony or maintenance 

1. If you suspect that this child was not born to you, you may file a petition to disclaim the paternity of the child and may pray for DNA test for paternity. 

2. In paternity testing DNA allows positive determination of parenthood.

But in recent case in 2001 supreme court refused to rely upon the result of DNA test and held that under section 112 of Indian evidence act,  non access between the man and woman is the only way to raise presumption against legitimacy. 

The dilemma of the court is that accepting DNA as evidence of legitimacy is likely to render many children illegitimate and many women uncharted.

Hence your petition may not be decided favorably by court. 

3. If you can prove that she is employed and drawing a handsome salary then you can deny maintenance or at least you should prove before court that she has sufficient means of income to sustain her expenses to repudiate her maintenance claim. 

However you would be liable to pay for child. 

1. You can get the DNA conducted if child is in your custody.

2. For the court to order DNA test of child there has to be a lis pending before the court pertaining to the paternity of child.

3. Maintenance has to be paid to wife unless you can prove that she is living in adultery or is earning sufficiently on her own.