One of my cats knew about my last pregnancy before there were any indications other than the production of hormones that made him feel insanely affectionate.
My cat told me the mailman just left.
My sister’s dog knew she was pregnant before she did. The dog always used to jump up on my sister to greet her, then suddenly mysteriously stopped. My sister then found out she was preggo. The dog continued to refrain from jumping...until after the baby was born, when she resumed.