Can Toddler's Predict Pregnancy?

My son is 2 years old and has always been very sweet and calm. Like all two year olds he does throw tantrums, but we have never before had any major problems. My husband and I have been thinking about having another child but wouldn't consider ourselves to be trying. We are not NOT trying. The last week at daycare my son has been a holy terror. Biting other kids, pulling hair, refusing to wear clothes, refusing to eat, even refusing to sit in time out. This is more than just a tantrum - its all day. He doesn't seem to have any physical discomfort and isn't teething. I don't think it is separation anxiety because he has been going to the same daycare since 3 months old.

The daycare recently called to let me know he was in trouble again and to ask if I might be pregnant. The daycare workers said that they have seen several instances where a child seems to do a 180 and have a terrible attitude in the first few weeks before the mom finds out she is pregnant again.

Has anyone ever heard of or experienced this before?