Prenatal screening for Down's syndrome with maternal serum human chorionic gonadotropin levels

Article Abstract:

Down's syndrome is a condition marked by mental retardation and other physical malformations caused by a defect in a chromosome, the genetic material in the nucleus of cells. The incidence of Down's syndrome is higher in babies born to women over age 35. Prenatal diagnosis performed because of increased maternal age detects 20 percent of fetuses with Down's syndrome. Many Down's syndrome children are born to younger mothers who do not have prenatal screening. Some studies have associated higher levels of alpha-fetoprotein (AFP) in the blood of the mother with increased risk for trisomy 21, Down's syndrome. In addition, a high level of the hormone human chorionic gonadotropin (hCG) has indicated an abnormal chromosome in 68 percent of cases. Researchers compared the results of a simple enzyme test for hCG beta subunit, performed on blood samples obtained from mothers of 38 Down's syndrome pregnancies and 114 normal pregnancies. Normal blood values of beta subunit hCG were not affected by age, race or weight but decreased each week from 15 to 19 weeks gestation. After the values were adjusted for gestational age, 63 percent of the fetuses with Down's syndrome were detected using this method. When the results of hCG and AFP were combined, the rate of correct diagnosis was 68.3 percent, and there was a decrease in the rate of false positive results from 14.8 percent to 5 percent (incorrectly reporting Down's syndrome). The AFP and beta subunit hCG tests appear promising as alternatives to the more invasive methods of prenatal diagnosis of Down's syndrome. The efficiency of the test methods is currently being improved.

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Triple marker (alpha-fetoprotein, unconjugated estriol, human chorionic gonadotropin) versus alpha-fetoprotein plus free-beta subunit in second-trimester maternal serum screening for fetal Down syndrome: a prospective comparison study

Article Abstract:

A blood screening test for the levels of three hormones in the second trimester of pregnancy may be more accurate than a modified test in detecting Down syndrome in fetuses. The triple-marker blood screening test measures the levels of alpha-fetoprotein (AFP), unconjugated estriol, and human chorionic gonadotropin (hCG). The modified test measured AFP and free beta-hCG on the speculation that free beta-hCG may be a better indicator of Down syndrome. Researchers compared the accuracy of the blood tests in 2349 nonblack women, taking maternal age into account. The test using AFP and free beta-hCG was found to detect fewer fetuses with Down syndrome while testing more women as being positive for the risk. hCG level may be the best predictor of Down syndrome of all the markers.

Estrogen, Estrogens

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Maternal serum analyte levels in pregnancies with fetal Down syndrome resulting from translocations

Article Abstract:

Maternal blood profiles appear to be similar in women carrying fetuses with Down's syndrome caused by either of two genetic conditions. One condition involves an extra copy of chromosome 21 called trisomy 21 or a shift of a chromosomal segment to the 21st chromosome called a Robertsonian translocation. Blood levels of alpha-fetoprotein, human chorionic gonadotropin, and unconjugated estriol were measured in 11 women carrying fetuses with a Robertsonian translocation. These values were compared with published levels for women carrying fetuses with trisomy 21. Both groups had similar values.

Birth defects, Blood, Blood chemical analysis

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