DIMERIC INHIBIN-A AND ALPHA-SUBUNIT IMMUNOREACTIVE MATERIAL IN MATERNAL SERUM DURING SPONTANEOUS AND IN-VITRO FERTILIZATION PREGNANCIES

To increase our understanding of the nature and source of immunoreacti ve inhibin-related material during pregnancy, we studied inhibin secre tion in women pregnant after spontaneous conception and after in vitro fertilization (IVF). Two solid phase enzyme-amplified immunoassays (E ASIAs) were used to measure the inhibin A dimer and inhibin alpha-subu nit immunoreactivities (alpha-inhibin). In spontaneous pregnancies, le vels of both inhibin A and alpha-inhibin were low during the first two trimesters of pregnancy, but a significant increase was observed towa rd the end of gestation. Both assays confirmed that inhibin concentrat ions in IVF pregnancies exceeded those in spontaneous pregnancies duri ng the entire first trimester. Moreover, the two assays displayed disc ordant profiles. The alpha alpha-EASIA, which detects all alpha-inhibi n immunoactivity, displayed a major peak during the follicular phase a nd a second broader peak during the luteal phase and corpus luteum res cue. A progressive decline was observed during the subsequent weeks. E ASIA measurements for inhibin A revealed distinct peaks during the fol licular phase, the luteal phase, and the hCG peak. A marked fall, howe ver, was seen at the time of corpus luteum rescue. In summary, these d ata indicate that the nature of the immunoreactive material changes co nsiderably during the different phases of pregnancy. The available evi dence further points to an ovarian source of dimeric inhibin in early pregnancy and a placental source toward the end of pregnancy.