Objective We aimed to measure the changes in serum P-LAP levels during different periods of pregnancy, and establish healthy RIs for clinicians. Methods Establish RIs for serum P-LAP between non-pregnant women and healthy pregnant women during first, second and third trimester. Results In controls the serum P-LAP RI was 33.68–56.83 U/L. Among healthy pregnant women, the P-LAP RI was 34.93–66.74 U/L in the first trimester, 69.58–200.34 U/L in the second trimester, and 76.31–408.71 U/L in the third trimester. Conclusion The RIs of serum P-LAP in healthy pregnant women providing RIs for clinical and laboratory work.