Ok, I'm gonna wade into this discussion with a for PN and also some advice, because I'm the Queen of Bits of Teeth Falling Off or even Breaking Right Through to the Root.

Yes, you are absolutely correct about pregnancy & teeth. Some calcium might not go astray BUT make sure your Vit D and your magnesium are topped up or you might as well peg pieces of chalk at your face for all the good it will do.

BETTER way to get calcium where it's needed (ie on the surface of your teeth, where it can prevent decay) is by using a product called Recaldent - tooth mousse. You can get it with or without the fluoride in, I prefer without. Also, you can have a toothpaste that's a bit more serious about the calcium than regular colgate. Ask your dentist about these.

In a similar vein, you can get Recaldent chewies, which are ace and help during the day if you're not towing a toothbrush around with you. BTW if your enamel is week, brushing too often can do more damage.

Finally, the grinding. Jaw muscles/face shape, yes. If you're unaware of this you're probably doing it in your sleep. My endodontist picked it before I even opened my mouth, subsequently (spectacularly) confirmed during a sleep study. I've had a mouth guard moulded that I wear to bed every night. Expensive but worth every penny.

Final tip - if your teeth are brittle, lay off the highly crunchy foods for a bit. Learn to suck your corn chips. And definitely never, ever, ever crunch ice.