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First-trimester maternal serum immunoreactive inhibin in chromosomally normal and abnormal pregnancies. Dutch Working Party on Prenatal Diagnosis.

OBJECTIVE
To investigate the maternal serum immunoreactive inhibin level in chromosomally normal and abnormal pregnancies in the first trimester.


METHODS
This was a retrospective study under the auspices of the Dutch Working Party on Prenatal Diagnosis. Maternal serum samples were taken before prenatal diagnosis. Forty-eight maternal serum samples from chromosomally abnormal pregnancies, including 23 with Down syndrome, were available for analysis; 284 samples from chromosomally normal pregnancies were used to establish reference ranges.


RESULTS
The median value of maternal serum immunoreactive inhibin in the 23 Down syndrome pregnancies was 1.3 multiples of the normal median (95% confidence interval 0.8-2.1). No significant difference was found between the distributions of the inhibin concentrations in the normal and the Down syndrome pregnancies or in the normal and the other chromosomally abnormal 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.