My doctor just suggested prescribing it to me for my reflux, and I'm in my third trimester.
I think your current doctor -- like many OB's -- goes by the theory that no pregnant woman should take meds during the first trimester. If at all possible. Sometimes, the real world intervenes.
Stand up for yourself and ask what alternative remedies she can recommend. Is this morning sickness or is it reflux? How does Pepcid AC treat morning sickness?