One of the most annoying things in the world is the fact that there are women who listen to men about feminine things. What am I talking about? Women who fast while pregnant because the Rebbeim say they should.
Rebbeim are a bit delusional in my opinion when it comes to pregnant women fasting. I can't quite grasp the logic. A woman that is pregnant CAN bend on many rules. She can eat milk after eating meat with a much shorter wait in between. A pregnant woman, is responsible for the life inside of her. She has to ensure the baby has the nutrients it needs, and the hydration to take away the toxins from her and her baby.
It is common knowledge that after Tsha B'av and Yom Kippur there are many premature births. This cannot possibly be a pro-fasting sign, or can it? Well, in the frum world, anything could be considered a good sign.
Ladies, if you're vomiting blue juice, don't be dumb, break your fast, especially if you're pregnant. Forget the Rabbis. Until they get ovaries and a uterus and bleed every month for a few years on schedule, they're not exactly the greatest advise givers.