Probably it has been said already several times (didn't fisnish reading the thread, sorry)
There is a current of thought that specifies that is better to speak to your children in your own language most of the time for several reasons. First you get child to learn the correct sounds of the language which are only naturally acquired during the first 3 years. Second, language is the main carrier of culture so, in multicultural situations it gives a child an understanding of himself and his family within the hosting cultural background. And third, spontaneity is a BIG issue, being able to be your natural self with your child is of paramount importance.
Any of the three things above may be compromised if you are speaking in a language foreign to you. However, it may be the case that you are submerged in that foreign language and it has become your own primary language while yours has taken a back seat, in such case it's OK.
In one hand, I have seen people who decide to speak their native language at home and let the children learn English at nursery/school. Their children are not behind at all in their mother language but obviously, they are in English. But, by 3-4 years old something clicks and they end up as fluent in English as they are in their own language. And due to the great exposure to the local language, the problem is no longer for them to speak the local language but for you to keep the mother language alive at home!
In the other hand, there are other parents who decide that the best start for their children (or possible for all the family) is to forget about their original language and concentrate in speaking the language of the place all the time. Contrary to what I was expecting, these children not only missed in learning the language of the parents, but had plenty of problems to speak the local language too, sometimes even more than those children whose parents spoke their own language at home. But again, by the time they are three or four... they are fine.
So... if you were just about to start I would recommend to leave it, but by now, perhaps speaking French to your child is so natural that it may be worth it to continue. In any case, no matter how much or little you try, their use of the local language will be as good as that of the other children that are around them, pretty soon.
Good luck.