The reason for 9 month waiting clause is as follows: Insurance is taken / given for an unforeseen / unpredictable event that may happen in future. In case a female is already pregnant when the maternity cover is granted then the logic of unforeseen / unpredictable does not hold good. Hence a claim is not accepted.
The method used in this case is to see the date of Last Menstrual Period (LMP). In case the LMP was before the date the cover was taken then the claim is denied but in case the LMP was after the cover was incepted, the claim thus arising is payable under the terms of the policy.
There fore you need to check two things (a) The cover inception date for your family which your office will be able to give to you and (b) check with your wife's doctor on the LMP date.
As mentioned above if the date of cover inception is before the LMP then your claim is payable in full amount.