If your income changes due to any additions to your family, then you will need to speak to your IP to get a variation agreed with your creditors.
If you can still manage to pay what you are paying now, then I doubt anything will change.
Sharing from experiences of dealing with debt
The greatness of a man is not in how much wealth he acquires, but in his integrity and his ability to affect those around him positively.
Bob Marley. http://kallis3.blogs.iva.co.uk
If you are in a position to get third party funds now may b a good time to offer a full and final. The loss of income due to maternity and the additional costs of a child could put a strain on your finances and creditors may look favourably on a settlement. If this is not possible do as Jan says and speak to your IP. You will need to calculate the extra income and expenses to see how your payments would be affected. The IVA will not prevent you from atarting a family and all issues should be resolved.