DISTRIBUTION OF IRON AND IRON-BINDING PROTEINS IN FIRST-TRIMESTER HUMAN PREGNANCIES

Objective: To investigate the iron distribution between the maternal a nd embryonic compartments in the first trimester of pregnancy. Methods : Coelomic and amniotic fluids (AF) and maternal serum were collected from 36 apparently normal pregnancies at 7-13 weeks of gestation. Iron , transferrin, ferritin, and lactoferrin were measured in all samples. Iron concentrations were also measured in placental villi, liver, gut , and brain samples collected from two embryos. Results: Significantly (median value) lower iron and transferrin levels and higher levels of ferritin were found in the coelomic fluid (iron 4.8 mu mol/L; transfe rrin 0.22 g/L) than in maternal serum (iron 21 mu mol/L; transferrin 2 .5 g/L). The AF contained significantly lower levels of iron and ferri tin (iron less than 1.8 mu mol/L; ferritin 2.0 mu g/L) than both coelo mic fluid (iron 4.8 mu mol/L; ferritin 287 mu g/L) and maternal serum (iron 21 mu mol/L; ferritin 49 mu g/L). Transferrin was undetectable ( less than 0.08 g/L) in AF samples, and lactoferrin was undetectable (l ess than 2 mu g/mL) in both embryonic fluids. The iron concentration i n the coelomic fluid increased significantly (P <.001) with advancing gestation (iron at 7-9 weeks 3.8 mu mol/L; 9.1-11 weeks 5.9 mu mol/L). There was a nonsignificant correlation between coelomic fluid and mat ernal serum iron and iron-binding protein levels. The highest iron lev els were found in the liver (52 mmol/kg dry weight) and brain (49 mmol /kg dry weight) tissues. Conclusions: The distribution of iron and iro n-binding proteins between the maternal and embryo-placental compartme nts in the first trimester is comparable to that found later in gestat ion, suggesting that placental iron transfer may occur as early as ter tiary villi are formed. The exocoelomic fluid is probably the main iro n reservoir in early pregnancy, and the secondary yolk sac is probably the principal route of entry of iron to the embryo.