The significance of maternal blood pregnancy-associated plasma protein A (PAPP-A) and free beta-subunit of human chorionic gonadotropin (β-hCG) levels for the risk assessment of fetal trisomy 18 during the first prenatal testing between 11 and 13+6 weeks of pregnancy.

Abstract

The aim of the study was to evaluate the significance of the maternal blood level of pregnancy-associated plasma protein A (PAPP-A) and free beta-subunit of human chorionic gonadotropin (β-hCG), to estimate the risk of fetal trisomy 18 and their correlation with the assessment of nuchal translucency (NT) during the first prenatal testing. Examinations of 93 pregnant women between 11 and 13+6 weeks of pregnancy were conducted, which included determination of β-hCG and PAPP-A concentrations in the maternal serum and ultrasound assessment of fetal nuchal translucency. Concentrations of biochemical parameters were expressed as multiples of median (MoM) for the appropriate gestational age. The risk assessment of trisomy 18 was analyzed using Astraia software. Pregnant women with a high (≥ 1:300) risk of trisomy 18 were offered a genetic amniocentesis with an examination of fetal karyotype. Twenty cases were healthy and 23 with trisomy 18. PAPP-A and β-hCG MoM values < 0.3 were found in 61% cases of fetal trisomy 18. In 26% of cases, PAPP-A and β-hCG MoM values < 0.2 were NT-independent risk factors for trisomy 18. There were no significant differences between groups with normal fetal karyotype (40%) and trisomy 18 (35%) in PAPP-A and β-hCG MoM 0.2-0.5 range. Maternal free β-hCG MoM was found to change parallelly to fetal NT widening in case of trisomy 18 diagnosis. Maternal β-hCG and PAPP-A MoM results presented less then 0.2 might be used independently of NT widening in fetus for trisomy 18 risk evaluation. Above 0.2 for PAPP-A and β-hCG MoMs, fetal NT measurement was an requirment.