How to spot a Reptilian Humanoid next to a pregnant lady in the metro

Concerned humans everywhere have bombarded me with secret email asking, nay, begging me to continue these posts on the threat of Reptilian Humanoids everywhere. Some of these emails have been death threats, but I'm not scared, I'm taking it like the real woman that I am.
First of all, an example. This is a reenaction of something I saw in the metro today. Please read carefully, your survival is at stake.
Pregnant lady entered the train. Nobody got up to give her a seat (don't look at me, I was standing too). She leaned against the window and sighed pointedly (subliminal for: "get off your asses you jerks, can't you see I'm pregnant!")
Reptilian Humanoid disguised as a young male human shouted: "That's what you get for being a slut!"
Pregnant gal: "Well, in that case, so was your mother." (superliminal for, "screw you, you loony.")
I tried to make my way to the RH in order to dismember him and rip out his entrails before he had a chance to spawn, but the train stopped and the other passengers shoved him out the door. Idiots! When will they learn.
Sadly, nobody got up to let the Pregnant Gal sit.

Contrary to what Reptilian Humanoids would want you to believe, pregnant women are not evil. I'll grant you that they're scary, a constant reminder of what can happen to Reptile Squishers everywhere if we aren't careful, but they're good for society for so many reasons.
There are several reasons why it's a good idea to let a Pregnant Woman have your seat in the metro.
1) It's polite, and it's a fast way of letting everyone know you care ie, you are not a Reptilian Humanoid in disguise.
2) It can be a good way to strike up a conversation. Taking a Pregnant Woman out to dinner might be the only way to stop your friends from going around saying you're a virgin. This works specially well if you're a human male. It might also work if you are a female gyn, but then you don't score any ex-virginity points so there's really not much point in trying.
3) Everyone knows a Pregnant Woman can unload at any given moment. A 8 or 9 month Pregnant Woman is a bomb waiting to explode. The floor of the metro is hard: do you really want baby brains splattered all over your vintage shoes. I don't think so.
Think about it, there are no exit signs in the womb. If the Pregnant Woman is sitting down, the baby won't be able to see its way out and will hopefully stay put until you have a change to get off the train.