Effect of hypoxia on amniotic fluid erythropoietin levels in fetal rats.

Erythropoietin (EPO) levels in amniotic fluid and serum were measured in hypoxic (fraction of inspired oxygen, FiO2, 0.09) and posthypoxic (following a 24-hour period of hypoxia, FiO2 0.09) fetal rats on day 21 of gestation. Each of the study groups comprised 12-20 fetuses. Each of the control groups consisted of 21 or 22 fetuses. Fetal serum EPO levels at 3, 6, 9, 12, and 24 h of hypoxia were significantly higher than the control level. Amniotic fluid EPO levels at 9, 12, and 24 h of hypoxia were also significantly increased compared to the control level. Fetal serum EPO levels returned to baseline during the 12- to 48-hour period after hypoxia. During the 0- to 48-hour posthypoxic period, amniotic fluid EPO levels were significantly higher than the control level. These data demonstrate that rates of appearance and turnover of amniotic fluid EPO are different from those of fetal serum EPO.