Parathyroid hormone-related protein levels in maternal and cord blood

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.

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.

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.

Parathyroid hormone-related protein produced in the fetoplacental unit, the breast, or both can reach the maternal circulation.