Successful breeding of Pets?

My cat got pregnant on the first try when my Sim encouraged her to mate. For those having trouble, perhaps try using the lot trait for breeding. I haven't tried it, but it may help.

I didn't know what those hearts meant around my dog at first. I took her on a walk & took her off her leash & she took off. By the time I called her back & was trying to encourage her to mate with another dog...the option was grayed out, as she had already woohoo'd with some dog on her own. Just waiting to see if she's pregnant.