Mummy, don't eat a baby!

Yesterday DD had a day off nursery for her teacher training day, so today was another Monday, or so it felt.
Waking up, both me and OH were smiling and cheerful knowing we'd soon be able to start the journey to conception, and DD seemed to pick up on this quickly. At 6am she was full of beans, incapable of sitting still and running rings around her Daddy, who was unsuccessfully trying to drink coffee and locate the things he needed for work.
So I sat DD down and asked her if her best friend would be at nursery today. Her mum was overdue and showing signs of going into labour last week, and I haven't seen her for a few days so we assumed that she'd had her +1.
"N's mummy had a baby in her tummy" I told DD whilst she picked at her breakfast. "and N may have a new baby brother now, maybe you can ask her when you get to school?"
DD looked at me confused, she's only 3 so this is all very alien to her. "In her tummy ?"
I smiled, "Yes sweetheart, when a baby is coming, Mummy's tummy gets really big, and when its really big its nearly time for the new baby to live with them." I told her, in a bad attempt to keep it very simple.

"Oh mummy, don't eat a baby!" the look of horror on DD's face was a picture. I wish I'd had a camera handy. It was a cross of fear and disgust, and had me in hysterics for a few moments.
"Sweetheart, I won't eat a baby... a baby starts like a seed in mummy's tummy and then it grows big into a baby." I tried to explain.
"Then you sick it up and baby lives with us." she informed me matter-of-factly and I didn't have the heart to correct her. Maybe when she's much older.