A polymeric heart valve, comprising: a valve body having a central axis and comprising a conduit extending along the central axis from an inflow end to an outflow end; and at least three flexible leaflets extending from the body into the conduit, each of the leaflets defining an attachment curve with the body and each leaflet comprising a pair of free edges coming to a tip near the central axis of the body; wherein: respective pairs of the at least three leaflets each define a commissure located proximal the body; the at least three leaflets define: a partially open position at rest; a fully open position where the at least three leaflets deflect away from the central axis during forward blood flow along a direction from the inflow end to the outflow end; and a closed position where the at least three leaflets deflect toward the central axis during reverse blood flow along a direction from the outflow end to the inflow end, characterized in that each leaflet is characterized by at least a four point thickness profile, wherein: the first point in the profile is substantially located at the tip of the leaflet; the second point and the fourth point in the leaflet are substantially located at respective commissures; the third point is substantially located proximal the body substantially midway along the attachment curve between the second point and the fourth point, and the thickness at the first point is less than the thickness at the second point and the fourth point. a valve body having a central axis and comprising a conduit extending along the central axis from an inflow end to an outflow end; and at least three flexible leaflets extending from the body into the conduit, each of the leaflets defining an attachment curve with the body and each leaflet comprising a pair of free edges coming to a tip near the central axis of the body; wherein: respective pairs of the at least three leaflets each define a commissure located proximal the body; the at least three leaflets define: a partially open position at rest; a fully open position where the at least three leaflets deflect away from the central axis during forward blood flow along a direction from the inflow end to the outflow end; and a closed position where the at least three leaflets deflect toward the central axis during reverse blood flow along a direction from the outflow end to the inflow end, respective pairs of the at least three leaflets each define a commissure located proximal the body; the at least three leaflets define: a partially open position at rest; a fully open position where the at least three leaflets deflect away from the central axis during forward blood flow along a direction from the inflow end to the outflow end; and a closed position where the at least three leaflets deflect toward the central axis during reverse blood flow along a direction from the outflow end to the inflow end, a partially open position at rest; a fully open position where the at least three leaflets deflect away from the central axis during forward blood flow along a direction from the inflow end to the outflow end; and a closed position where the at least three leaflets deflect toward the central axis during reverse blood flow along a direction from the outflow end to the inflow end, characterized in that each leaflet is characterized by at least a four point thickness profile, wherein: the first point in the profile is substantially located at the tip of the leaflet; the second point and the fourth point in the leaflet are substantially located at respective commissures; the third point is substantially located proximal the body substantially midway along the attachment curve between the second point and the fourth point, and the thickness at the first point is less than the thickness at the second point and the fourth point. the first point in the profile is substantially located at the tip of the leaflet; the second point and the fourth point in the leaflet are substantially located at respective commissures; the third point is substantially located proximal the body substantially midway along the attachment curve between the second point and the fourth point, and the thickness at the first point is less than the thickness at the second point and the fourth point.