I think it depends on both yours and your spouses contribution to taking care of the child. It also depends what number child you are on like ericb said. The first child is always the hardest and can be a distraction for a couple of months. After those couple of months, and even if you have more children the distraction becomes a need to support your family over your startup. If you can fund your startup and your family without making them suffer, AND you have a supportive spouse in terms of the hours you have to put into your startup, then you are all set.

Edit: I just noticed your user name is kia, so there is a high probability that you are female. Although it is not exactly "right" it is "traditionally" expected for a woman to be more of a contributor to taking care of the child than the man. Thus, it depends greatly on your spouses willingness to forgo gender bias and help you. I would suggest that you be very open and thorough in your communication about how you will share the responsibilities of the child.