title: On the origin of amniotic fluid bilirubin.
abstract: We studied the relationship between bilirubin concentrations in amniotic fluid and fetal blood in 68 non-hydropic rhesus d-alloimmunized anemic fetuses at first blood sampling. In these alloimmunized fetuses, the amniotic fluid/fetal blood ratio for bilirubin decreased from 0.09 at 28 weeks to 0.05 at 33 weeks. In normal fetuses, amniotic fluid/fetal blood ratios for bilirubin, and for albumin, are in the same range and show a similar decrease during gestation. We conclude that amniotic fluid bilirubin concentration is determined, firstly, by fetal blood bilirubin concentration and, secondly, by the amniotic fluid/fetal blood ratio of albumin. Among five possible pathways bilirubin could take to build up a concentration in amniotic fluid (fetal kidneys, lungs, skin, bowel, membranes), the intramembranous pathway is the only one that is compatible with the amniotic fluid/fetal blood ratios for bilirubin that we found and must therefore be the most important.
authors.affiliation: Department of Obstetrics and Gynecology, K6-32, Leiden University Medical Center, P.O. Box 9600, 2300 RC Leiden, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Sikkel
authors.forename: S A
authors.initials: SA
authors.lastname: Pasman
authors.forename: D
authors.initials: D
authors.lastname: Oepkes
authors.forename: H H H
authors.initials: HH
authors.lastname: Kanhai
authors.forename: F P H A
authors.initials: FP
authors.lastname: Vandenbussche
mesh_terms: D000653:Amniotic Fluid / Q000737:chemistry / Q000378:metabolism*; D001663:Bilirubin / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D001692:Biological Transport; D005321:Extraembryonic Membranes / Q000378:metabolism; D005312:Fetal Blood / Q000737:chemistry / Q000378:metabolism*; D005865:Gestational Age; D006454:Hemoglobins / Q000032:analysis / Q000378:metabolism; D006801:Humans; D012203:Rh Isoimmunization / Q000097:blood / Q000378:metabolism; D012709:Serum Albumin / Q000032:analysis / Q000378:metabolism
chemical_list: D006454:Hemoglobins; D012709:Serum Albumin; D001663:Bilirubin