Secrets

So my heroine has a secret and I'm wondering when she should reveal it. I'm reading a secret baby book and the reader knows, but the hero doesn't. It's causing some tension as I'm wondering when she's going to reveal it and what his reaction will be when he finds out.

I'm wondering if I should let my readers in on the heroine's secret earlier, and let them feel the same tension, and maybe have some questions about the heroine's motivation at the same time.

Does that work for you? Knowing a secret that the character is keeping from the other main character?