Multiple marker screening test: identification of fetal cystic hygroma, hydrops, and sex chromosome aneuploidy

Lack of correlation between elevated maternal serum hCG during second-trimester biochemical screening and fetal congenital anomaly

OBJECTIVE

Isolated elevations in midtrimester maternal serum human chorionic gonadotrophin concentrations (MShCG) have been reported to be associated with a substantially increased likelihood of fetal congenital malformations. The reported malformations included a wide range of organ systems, originating at different embryologic developmental stages. The purpose of our study was to determine the significance of an isolated elevated MShCG (>2.5 MoM) in midtrimester for the detection of fetal structural anomalies in a large population.

METHODS

Among 10,144 women who underwent a biochemical triple screen at 15 to 18 weeks' gestation, 463 patients, who had an elevated MShCG, but normal alpha-fetoprotein (AFP) and unconjugated estriol (uE3) levels, were identified. Patients with an integrated calculated Down syndrome risk above 1:250 were excluded. Only nonsmokers, at ages <35 years, without a history of prior fetal anomalies were included. The control group consisted of 463 patients with normal serum analyte concentrations and Down syndrome risks below 1:250, who were matched for maternal age and date of biochemical screen. All patients underwent a detailed genetic sonogram in which an anatomic survey and multiple 'soft markers' for aneuploidy were looked for. Newborns were examined by a senior pediatrician trained in dysmorphology.

RESULTS

MShCG levels were 3.18 +/- 0.72 versus 0.99 +/- 0.43 MoM (p < 0.0001) in study and control groups respectively. Sonography revealed 8 versus 6 cases of major congenital anomalies among the 463 patients of their respective groups, and 39 versus 36 sonographic 'soft markers' for aneuploidy. Fetal karyotyping and neonatal examination for dysmorphology revealed 6 chromosomal anomalies (4 Down syndrome; 2 Turner syndrome) among the 8 major malformations in the study group, but none in the controls (p < 0.0001). Three of the 39 fetuses with 'soft markers' and elevated MShCG were found to have trisomy 21.

CONCLUSION

Isolated elevation of MShCG does not confer an increased risk of fetal congenital anomalies other than chromosomal abnormalities. However, elevated MShCG levels in combination with sonographic 'soft markers' for aneuploidy were associated with a high incidence of chromosomal anomalies, despite a normal biochemical triple screen risk estimate.

Phenotype, ovarian function, and growth in patients with 45,X/47,XXX Turner mosaicism: implications for prenatal counseling and estrogen therapy at puberty

OBJECTIVE

Our objective was to determine whether girls with the rare Tur-ner 45,X/47,XXX mosaic karyotype are less severely affected than girls with 2 commoner karyotypes.

STUDY DESIGN

We evaluated growth status, phenotype, and ovarian function in 7 girls with 45,X/47,XXX mosaicism, age-matching each with 2 girls with 45,X and 1 with 45,X/46,Xi(X)(q10) karyotypes.

RESULTS

For the index, 45,X, and 45,X/46,Xi(X)(q10) groups, respectively, the median/mean height SD score at the start of growth hormone therapy/comparable age was -2.0 (-1.2), -2.3 (-2.4), and -2.6 (-2.6), cardiac anomalies were identified in 0 of 7, 4 of 14, and 1 of 7, renal abnormalities in 0 of 7, 4 of 14, and 3 of 7, middle ear problems in 2 of 7, 11 of 14, and 4 of 7, and special educational needs in 0 of 7, 3 of 14, and 1 of 7. Complete spontaneous puberty with menarche was seen in all but 1 girl older than 12 years in the index group compared with only 1 girl in the comparison groups. Ovarian tissue was identified in 6 of 7, 0 of 14, and 1 of 7 girls, and the mean follicle-stimulating hormone was 6, 25, and 21 U/L, respectively.

CONCLUSION

Girls with 45,X/47,XXX karyotype are mildly affected, with good preservation of ovarian function. This result has important implications for prenatal counseling and the need for estrogen therapy at puberty.

Maternal serum alpha-fetoprotein and dimeric inhibin A detect aneuploidies other than Down syndrome

OBJECTIVE

Our purpose was to determine whether the combination of maternal serum alpha-fetoprotein, free human chorionic gonadotropin-beta, dimeric inhibin A, and maternal age detects aneuploidies other than Down syndrome.

STUDY DESIGN

We retrieved stored serum from pregnancies complicated by aneuploidies other than Down syndrome from 1988 to 1997 (n = 55, mean maternal age 35.2 +/- 5.6 years). Alpha-fetoprotein levels were obtained from our database, and free human chorionic gonadotropin-beta and dimeric inhibin A levels were measured in the thawed serum with use of commercial assays. Analyte values were used in both 3-analyte and 2-analyte multiple-marker screening tests; detection rates were determined at several different Down syndrome risk-positive cutoff values.

RESULTS

In the 3-analyte test 58% (32/55) of all aneuploidies were detected with use of both the Down syndrome protocol at a screen-positive risk cutoff value of 1:300 (false-positive rate 17%) and a novel trisomy 18 screening algorithm. However, 67% (37/55) detection was obtained with use of the 2-analyte combination of alpha-fetoprotein and dimeric inhibin A, with both the Down syndrome protocol (screen positive cutoff value 1:300) and the trisomy 18 algorithm: 12 of 13 trisomy 18 (92%), 9 of 17 Turner's syndrome (53%), 10 of 17 other sex chromosome aneuploidies (59%), 1 of 1 trisomy 22 (100%), and 5 of 7 trisomy 13 (71%).

CONCLUSIONS

The combination of maternal serum alpha-fetoprotein, dimeric inhibin A, and maternal age detects autosomal trisomies other than Down syndrome at a rate superior to that of the traditional analyte combination.