Pregnant Heart Murmur

At the beginning of my last pregnancy (which ended in miscarriage at 6 weeks), my doctor heard a heart murmur.  I had an echocardiogram done which stated the following:
Left ventricular systolic function is normal with an ER of 55-60%
Left ventricular size is normal.
Left atrium is normal in size and function.
Mitral valve is normal.
Mild mitral regurgitation is present.
Aortic valve is trileaflet and appears structurally normal.
Mild tricuspid regurgitation is present.

About a month after the miscarriage, no murmur was heard during my normal exam.

I am now pregnant again and the murmur is back.  My doctor has stated that it is an innocent murmur, but I am nervous about it.  Could the mild regurgitation be a problem in my pregnancy or in general?  I should mention that during my first pregnancy, I developed preeclampsia at 38 weeks and had severe post partum hypertension that was successfully treated with medication and subsided completely (off meds) by 4 months postpartum.  No murmur was ever mentioned to me during that pregnancy.

Should I be concerned about this current regurgitation?  Should I be seeing a cardiologist throughout this pregnancy?

[Cleveland Clinic]

I can't comment on the present murmur, but I have no reason to dis-believe your doctor who examined you and told you it is an innocent murmur. Pregnant women have high cardiac outputs which can bring out innocent murmurs, or even created artificial sounds which sound like murmurs such as venous hums.
Mild mitral regurgitation is not associated with a high risk pregnancy, and apart from possibly requiring antibiotics at the time of delivery, probably had nothing to do with you unfortunate prior outcome. Even this recommendation is now in question based on the most recent guidelines.