Can pregnancy cause a heart murmur?

It's common: Your cardiac output increases greatly, and a physician with good ears can hear any turbulence in the heart that this wil produce. If your physician isn't concerned, i would not be either.

Yes: Blood volume increases during pregnancy and a pregnant woman can develop a "flow"/innocent murmur assuming she has a structurally normal heart. If she has any structural abnormalities, then some murmurs may become more apparent.