Inhibin-B and pro-αC-containing inhibins in amniotic fluid from chromosomally normal and down syndrome pregnancies

Euan M. Wallace, Jennifer A. Crossley, Simon C. Riley, Claire Balfour, Nigel P. Groome, David A. Aitken

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In second-trimesler Down syndrome pregnancies, levels of inhibin-A (the α-β(A) dimer) in maternal serum and amniotic fluid (AF) are significantly higher and lower than in normal pregnancy, respectively. Since AF also contains inhibin-B (the α-β(B) dimer) and precursor inhibins, we have examined whether the secretion of these inhibin isoforms may also be altered in association with Down syndrome. AF from 45 Down syndrome and 150 chromosomally normal pregnancies between 16 and 19 weeks' gestation were analysed, blinded to whether the sample was from a Down syndrome or a normal pregnancy. The median (10th-90th percentiles) inhibin-B level in the control pregnancies increased from 310.0 (80.8-1112.5) pg/ml at 16 weeks to 459.5 (193.7-1386.8) pg/ml at 19 weeks' gestation. The corresponding figures for precursor inhibins (pro-αC inhibins) were 541.8 (206.9-1322.8) pg/ml at 16 weeks and 1391.8 (433.3-2652.6) pg/ml at 19 weeks. Expressed as multiples of the median (MOM), the levels of inhibin-B and pro-αC inhibins in the Down syndrome samples were 0.85 and 0.79, respectively. Neither was significantly different from the controls. These data suggest that, of the three inhibin subunits, abnormal production or secretion of the inhibin β(A)-subunit may underlie the decreased inhibin-A levels previously observed in Down syndrome. Confirmation of this by quantitative assessment of the inhibin subunit messenger ribonucleic acids would now be useful.

Original languageEnglish
Pages (from-to)213-217
Number of pages5
JournalPrenatal Diagnosis
Issue number3
Publication statusPublished - Mar 1998


  • Amniotic inhibins
  • Down syndrome
  • Inhibin A and B
  • Pro-αC inhibins

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