I have finally responded to them, waiting for their response. I wish to extend my gratitude to all those who contributed to this thread. I will post their response here when I get it.

I was the one that told them i have a new dependent, they did not find out. I have also given them the birth certificate and paid for the processing fee. I will abide with whatever decision is reached by the IO, I do not have any choice anyway.

I was the one that brought it to their notice, anyway, I will tell them the truth, if the IO is not convinced, there is really nothing I can do about it but to accept the decision. Life Continues.

Thanks everyone for your input, much appreciated. I was afraid they might say I misrepresented.

I applied for Canadian Immigration Visa last year and listed my wife and two children as dependents. Early this year my wife gave birth to a baby girl and later in the year we were asked to refill the forms by CIC, unfortunately, I did not list my last child as a dependent thinking wrongly that since she was not in the original application, she will only be added after the visa was granted. In October, we were asked to go for Medicals and going through the instructions I discovered my mistake and quickly sent a mail to CIC informing them of the new dependent, I was asked to bring her details which I did, now, I have received a mail from them asking me to explain why she was not included in the forms early this year, I intend telling them the truth about my mistake but will like people to tell me what their response is usually like in a situation like this.