Be careful to listen for WHAT exactly they asked. The first time mine did this I sighed and started this long conversation. My son finally rolled his eyes and said Mooooom, I meant from the front or the back. LOL. From the front.Okay and he was gone. He asked another ?? about 4 months later. As parents we are ready to go into 'the talk' and they may want to know if a baby comes from inside Mommy or is the kid telling the stork story lying. There are some really great books that are age appropriate to help you talk with your kids about it too.
Well, my daughter hasn't asked but she told me! She asked why our friend wanted to get pregnant. I told her because she wanted a baby! She said, yep! And SH\he prayed that she would have a baby and she fell asleep and she went to the doctor and God used his powers and made her pregnant and she didn't even know it! I thought that was a wonderful answer!
I bought "The Flip-Flap Body Book" to read with my son whenever he asks questions like this. We've talked a lot about how he was a baby in my womb, he's seen pictures of babies growing inside, we've talked about sperm from daddy and egg from mommy, but no details on how they go about combining. The book also helped him learn where poop and pee come from.