Maternal serum inhibin-A and free beta-hCG concentrations in trisomy 21 pregnancies at 10 to 14 weeks of gestation.
OBJECTIVE
To determine the relation between maternal serum inhibin-A and free beta-hCG concentrations in chromosomally normal pregnancies and to compare the two biochemical markers for their sensitivity in identifying trisomy 21 pregnancies.


METHODS
Inhibin-A and free beta-hCG were measured in maternal serum samples from 800 chromosomally normal singleton pregnancies at 10 to 14 weeks of gestation and 76 singleton pregnancies with fetal trisomy 21.


RESULTS
In the normal group maternal serum inhibin-A was significantly associated with both maternal weight and gestational age (F = 11.2, P < 0.0001). In pregnancies with trisomy 21 the maternal serum inhibin-A and free beta-hCG concentrations were significantly increased (mean difference inhibin = 0.51 SD, F = 18, P < 0.0001 and mean difference free beta-hCG = 1.13 SD, F = 80, P < 0.0001). For a 5% false positive rate, the sensitivity of maternal serum free beta-hCG in identifying pregnancies with trisomy 21 was 28.9% compared with 12.8% for maternal serum inhibin-A. Delta inhibin-A was significantly associated with delta-free beta-hCG (r = 0.345, P < 0.01) and the deviation from the normal mean for free beta-hCG was significantly greater than the deviation for inhibin-A (t = 4.0, P < 0.0001). For a 5% false positive rate, the sensitivity achieved by combining information from delta inhibin-A and delta free beta-hCG was similar to the sensitivity of free beta-hCG alone (30.3% compared with 28.9%).


CONCLUSIONS
At 10 to 14 weeks of gestation fetal trisomy 21 is associated with increased maternal serum inhibin-A and free beta-hCG levels. However, the degree of elevation of inhibin-A is less than that of free beta-hCG, and there is a significant association between levels of the two proteins. The sensitivity for trisomy 21 achieved with the combination of maternal serum inhibin-A and free beta-hCG is not significantly different from that achieved with maternal serum free beta-hCG alone.
Noble
P L
PL
Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London, UK.
Wallace
E M
EM
Snijders
R J
RJ
Groome
N P
NP
Nicolaides
K H
KH
D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D001835:Body Weight; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood*; D004314:Down Syndrome / Q000097:blood*; D005260:Female; D005865:Gestational Age; D006801:Humans; D007265:Inhibins / Q000097:blood*; D008875:Middle Aged; D011247:Pregnancy; D011261:Pregnancy Trimester, First
D015415:Biomarkers; D018997:Chorionic Gonadotropin, beta Subunit, Human; D007265:Inhibins