Before I was "in the know" about such things. My daughter's mother would dive while pregnant. In the first trimester, I didn't notice her having any difficulty or complaint, we didn't even know she was pregnant at that point (She's notorious for irregular cycles). In the second trimester, she barely had the energy to begin to make the trek through the surf zone. Watching this, I was horrified, she got knocked down, and the surf was on her. I rushed over, got behind her, held her reg in her mouth and dragged her back. She didn't have the energy to gear down. I ended up removing her gear and putting it away while monitoring her. That was her last dive pregnant. Some may ask "why did you let her dive"? I can answer that with an easy "No one lets or doesn't let her do anything" she's too strong willed. Others may ask "Why did you dive with her"? That's easy to answer too, I wanted to be there, in the back of my mind, if anything did happen, I trust myself more than I trust anyone else in a pinch. I'll say this, I found it amusing watching a pregnant woman stuff herself in a 7mm wetsuit. Got to give her top marks for THAT accomplishment.
-Dennis