Distribution of iron and iron-binding proteins in first-trimester human pregnancies.
OBJECTIVE
To investigate the iron distribution between the maternal and 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 mumol/L; transferrin 0.22 g/L) than in maternal serum (iron 21 mumol/L; transferrin 2.5 g/L). The AF contained significantly lower levels of iron and ferritin (iron less than 1.8 mumol/L; ferritin 2.0 micrograms/L) than both coelomic fluid (iron 4.8 mumol/L; ferritin 287 micrograms/L) and maternal serum (iron 21 mumol/L; ferritin 49 micrograms/L). Transferrin was undetectable (less than 0.08 g/L) in AF samples, and lactoferrin was undetectable (less than 2 micrograms/mL) in both embryonic fluids. The iron concentration in the coelomic fluid increased significantly (P < .001) with advancing gestation (iron at 7-9 weeks 3.8 mumol/L; 9.1-11 weeks 5.9 mumol/L). There was a nonsignificant correlation between coelomic fluid and maternal serum iron and iron-binding protein levels. The highest iron levels were found in the liver (52 mmol/kg dry weight) and brain (49 mmol/kg dry weight) tissues.


CONCLUSIONS
The distribution of iron and iron-binding proteins between the maternal and embryo-placental compartments in the first trimester is comparable to that found later in gestation, suggesting that placental iron transfer may occur as early as tertiary villi are formed. The exocoelomic fluid is probably the main iron reservoir in early pregnancy, and the secondary yolk sac is probably the principal route of entry of iron to the embryo.
Gulbis
B
B
Department of Clinical Chemistry, Hôpital Erasme, Brussels, Belgium.
Jauniaux
E
E
Decuyper
J
J
Thiry
P
P
Jurkovic
D
D
Campbell
S
S
D000653:Amniotic Fluid / Q000378:metabolism*; D001826:Body Fluids / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D003430:Cross-Sectional Studies; D004622:Embryo, Mammalian / Q000378:metabolism*; D005260:Female; D005293:Ferritins / Q000378:metabolism; D005333:Fetus / Q000378:metabolism*; D006801:Humans; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins; D007781:Lactoferrin / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D011261:Pregnancy Trimester, First / Q000378:metabolism; D011990:Receptors, Transferrin / Q000378:metabolism*; D014168:Transferrin / Q000378:metabolism; D033863:Transferrin-Binding Proteins
D002352:Carrier Proteins; D033862:Iron-Binding Proteins; D011990:Receptors, Transferrin; D014168:Transferrin; D033863:Transferrin-Binding Proteins; D005293:Ferritins; D007501:Iron; D007781:Lactoferrin