Do you modify the albumin level below which you would prophylactically anticoagulate a pregnant patient with nephrotic-range proteinuria, given that hypoalbuminemia is expected in pregnancy?  

I wouldn't anticoagulate for nephrotic syndrome unless the albumin was <2.5, and that is too low for pregnancy. Besides, "any" pregnant patient with "any" renal disease should be on ASA for preeclampsia prophylaxis. So, all pregnant patients with proteinuria need ASA (not without anticoagulation ...