[Serum concentrations of delta 5C21 steroids during pregnancy and at delivery]

In order to study the changes of C21-steroid levels which included Pregnenolone (P5), 20 alpha dihydropregnenolone (20P5), 16 alpha hydroxypregnenolone (16P5), progesterone (P4) and 20 alpha dihydroprogesterone (20P4) in maternal peripheral blood during pregnancy and at delivery, these steroids were measured by GC-MASS with application of deuterated steroids as internal standard. The accuracy of GC-MASS method of these steroids was satisfactory with C.V. value of less than 6%. Total delta 5C21 steroid concentrations in course of pregnancy and at delivery were as follows; P5 (mean +/- S.D. ng/ml): 66.6 +/- 36.2 (1st trimester), 80.9 +/- 24.6 (2nd trimester), 147.7 +/- 30.1 (3rd trimester) and 299.7 +/- 178.3 ng/ml (at delivery), 20Ps: 212.6 +/- 102.5, 143.4 +/- 53.9, 248.9 +/- 58.8, 563.4 +/- 198.2 ng/ml, 16P5: 8.6 +/- 8.6, 8.1 +/- 5.2, 124.3 +/- 40.3, 378.5 +/- 180.0 ng/ml, respectively. P4 (43.0 +/- 28.0 ng/ml) and 20P4 (8.0 +/- 4.0 ng/ml) in 1st trimester showed gradual increase to maximum level (P4: 138.2 +/- 30.1 ng/ml, 20P4: 105.4 +/- 21.6 ng/ml) at pre-pain period, afterward decreased rapidly (P4: 70.9 +/- 23.2 ng/ml, 20P4: 59.8 +/- 19.3 ng/ml) at delivery. P5, 20P5 and 16P5 levels were found to be significantly higher in umbilical artery (UA) as well as in umbilical vein (UV) than those in maternal vein (MV) regardless of labor pain. P4 and 20P4 did not show any differences in MV regardless of labor pain. P4 in UV (pain+) and 20P4 in UA (pain-), however, showed significantly higher than P4 in UV (pain-) and 20P4 in UA (pain+). P5, 20P5, 16P5 and 20P4 levels were significantly lower in the case of anencephalic pregnancy (ANC) at 3rd trimester than in normal pregnancy, especially 16P5 levels (22.2 +/- 5.0 ng/ml) showed 1/5 of those in normal pregnancy. From the results obtained above, it is suggested that these delta 5C21 steroids are actively produced in the feto-placental unit in the course of pregnancy. The levels of these steroids reached maximum at delivery, but the levels of P4, 20P4 decreased toward delivery after maximum levels were shown in the stage of pre-labor pain. No significant difference of P4 level in the case of ANC suggested that P4 production correlated with placenta as well as maternal and fetal precursor. Decreasing of 20P4 and P4 level after the stage of pre-labor pain suggested that activity of 3 beta hydroxysteroid dehydrogenase was reflected by uterine contraction during labor.