Parathyroid hormone-related protein levels in maternal and cord blood

OBJECTIVE: Our purpose was to determine the plasma levels of parathyroid hormone-related protein in normal pregnant women in each trimester, at 1 month post partum in women using different feeding methods, and in umbilical venous blood. STUDY DESIGN: We studied 40 healthy nonpregnant women, 90 healthy pregnant women (30 in the each trimester), and 140 postpartum women (breast-feeding 74, mixed feeding 33, bottle feeding 33). We also measured the parathyroid hormone-related protein level in umbilical venous blood in 24 women. RESULTS: The means and SDs of the plasma parathyroid hormone-related protein level were 1.04 +/- 0.11 pmol/L (0.81 to 1.26 pmol/L) in nonpregnant women, 1.06 +/- 0.19 pmol/L (0.69 to 1.48 pmol/L) in pregnant women in the first trimester, 1.10 +/- 0.19 pmol/L (0.80 to 1.50 pmol/L) in pregnant women in the second trimester, and 1.17 +/- 0.16 pmol/L (0.86 to 1.57 pmol/L) in pregnant women in the third trimester. At postpartum month 1 the plasma level of parathyroid hormone-related protein was 1.25 +/- 0.23 pmol/L (0.83 to 2.01 pmol/L) in breast-feeding women, 1.17 +/- 0.16 pmol/L (0.84 to 1.53 pmol/L) in mixed-feeding women, and 1.03 +/- 0.16 pmol/L (0.74 to 1.43 pmol/L) in bottle-feeding women. The umbilical venous blood level of parathyroid hormone-related protein was 1.33 +/- 0.32 pmol/L (0.84 to 2.11 pmol/L). The mean plasma level of parathyroid hormone-related protein increased throughout pregnancy and was significantly high in the third trimester and closely associated with the degree of breast-feeding at 1 month post partum. The parathyroid hormone-related protein level in umbilical venous blood was significantly higher than those in any groups of pregnant women. CONCLUSIONS: Parathyroid hormone-related protein produced in the fetoplacental unit, the breast, or both can reach the maternal circulation.