I did that once at a birthday party. 21 weeks pregnant and someone asked when I was due. The look of horror was priceless. I had a good laugh and so did she. Her friends were in the toilets (ladies public bathroom) just about, or maybe did, wet themselves from laughing at the overheard conversation.
You greatly overestimate the competency of TSA rent-a-cops.
Though, the mentioned suggestion would absolutely fail considering most airports do x-rays now. Also, if you're pregnant, kinda want to disclose that due to the whole x-ray thing.