I donate plasma regularly, but I'm beginning to think that I might be pregnant. It's too early to take a test, so my question is, would it be harmful to the fetus if I continue to donate, if it is the case that I am pregnant?

Given the mistakes during transfusions, i.e. STDs, AIDS, dirty needles. It happens. Would you want to take the chance ? I know I wouldn't. No matter how clean and professional the attendants appear to be, I just could not do it if I was pregnant.

Anyway, I don't think they allow pregnant women to donate blood.

Tick

I think it could be harmful to the fetus. When you are pregnant your blood volume increase because you and the baby need it. I would wait till I had a negative. Test to donate if I was you.

The American red cross strictly forbids donating blood while pregnant unless it is for your own use due to upcoming surgery.
It can deplete your iron reserve which is vital to the health of your unborn.

Given the mistakes during transfusions, i.e. STDs, AIDS, dirty needles.

It's easier to get these diseases from a simple tattoo, not so much transfusions since the 1980s.