MATERNAL SERUM PREGNANCY-ASSOCIATED PLASMA-PROTEIN-A AND FETAL NUCHALTRANSLUCENCY THICKNESS FOR THE PREDICTION OF FETAL TRISOMIES IN EARLY-PREGNANCY

Objective: To determine if the risk for fetal trisomies during the fir st trimester of pregnancy can be derived by combining data from matern al serum pregnancy-associated plasma protein A (PAPP-A) and fetal nuch al translucency thickness. Methods: pregnancy-associated plasma protei n A was measured in samples from 87 singleton pregnancies with fetal c hromosomal abnormalities (45 trisomy 21, 19 trisomy 18, eight trisomy 13, 11 sex chromosome aneuploidies, four triploidies) and 348 chromoso mally normal controls at 10-13 weeks' gestation. Likelihood ratios for trisomies 21, 18, and 13 in relation to PAPP-A, in multiples of the n ormal median (MoM) for crown-rump length, were derived from the overla pping gaussian frequency distribution curves for normal and abnormal p regnancies. Results: In the chromosomally normal group, maternal serum PAPP-A correlated significantly with fetal crown-rump length (r = 0.4 21, P < .0001). In the chromosomally abnormal group, the median PAPP-A was significantly lower than in the normal controls. The respective m edian values expressed in MoM for trisomies 21, 18, and 13 and other a neuploidies were 0.5 MoM (90% confidence interval [CI] 0.09-1.67, z = 6.0, P < .001), 0.17 MoM (90% CI 0.06-1.45, z = 6.6, P < .001), 0.25 M oM (90% CI 0.10-0.65 z = 4.5, P < .001), and 0.72 MoM (90% CI 0.09-2.4 8, z = 2.2, P < .05), respectively. There was no significant linear as sociation between PAPP-A and fetal nuchal translucency thickness in ei ther the chromosomally normal (r = -0.01, P = .89) or abnormal groups (r = -0.19, P = .08). Conclusion: The risks for fetal trisomies at 10- 13 weeks' gestation can be derived by combining data on maternal age, maternal serum PAPP-A, and fetal nuchal translucency thickness.