Figure 2: Box plot representations of plasma opiorphin levels in healthy young men (n=21), women (n=16) and pregnant women (n=8). Single individual values below the 10th or above the 90th percentile are represented as open circles. The box intersecting line represents the median and the box upper and lower limits represent the 75% and 25% percentile, respectively. **P<0.01 by MWT; (n) number of subjects.