Soluble transferrin receptor: longitudinal assessment from pregnancy to postlactation

To assess the impact of pregnancy and lactation on iron status and erythropoiesis as measured by the soluble transferrin receptor (sTfR).

We recruited women in early pregnancy to be followed for 2 years. We determined sTfR and sTfR/serum ferritin (sTfR/Fer) during puerperium (n = 77), lactation (n = 111), and postlactation (n = 57), with comparison to data obtained during pregnancy (n = 224). Data were evaluated using analysis of variance for repeated measures as the women continuing the study were found to be representative of those entering the study.

We found that sTfR and sTfR/Fer were significantly higher at all sampling occasions compared with early pregnancy (P <.001). Iron status markers did not regain first-trimester levels postpartum. Postlactation, 20% of the women had depleted iron stores (sTfR/Fer greater than 500), and 10% had tissue iron deficiency (sTfR greater than 8.3 mg/L). Iron status worsened with increasing parity and was significantly correlated to blood loss at delivery. In a subgroup of women with persistent adequate iron stores, first-trimester sTfR was similar to that in the puerperium but significantly lower than that postlactation. Cord sTfR (n = 32) was twice maternal sTfR and not correlated to maternal serum ferritin, gestational age, or other birth variables.

Our data show decreased erythropoiesis in early gestation and during the first week of the puerperium. To prevent a negative effect of childbearing on iron status, postpartum iron supplementation should be considered in women who bleed excessively at parturition and in those who choose to take a low dose of iron or none at all during pregnancy.