FIRST-TRIMESTER MATERNAL SERUM IMMUNOREACTIVE INHIBIN IN CHROMOSOMALLY NORMAL AND ABNORMAL PREGNANCIES

Objective: To investigate the maternal serum immunoreactive inhibin le vel in chromosomally normal and abnormal pregnancies in the first trim ester. Methods: This was a retrospective study under the auspices of t he Dutch Working Party on Prenatal Diagnosis. Maternal serum samples w ere taken before prenatal diagnosis. Forty-eight maternal serum sample s from chromosomally abnormal pregnancies, including 23 with Down synd rome, were available for analysis; 284 samples from chromosomally norm al pregnancies were used to establish reference ranges. Results: The m edian value of maternal serum immunoreactive inhibin in the 23 Down sy ndrome pregnancies was 1.3 multiples of the normal median (95% confide nce interval 0.8-2.1). No significant difference was found between the distributions of the inhibin concentrations in the normal and the Dow n syndrome pregnancies or in the normal and the other chromosomally ab normal pregnancies. Conclusion: In contrast to the second trimester of pregnancy, the level of maternal serum immunoreactive inhibin in the first trimester is not related to fetal chromosomal abnormalities and therefore is not useful as a biochemical screening index.