Objective: Pregnancy-associated plasma protein A has been reported to be low in Down syndrome affected pregnancies during the first trimester of pregnancy. The aim of this study was to determine preliminary the medians of pregnancy-associated plasma protein A (PAPP-A) in the first trimester of pregnancy and to compare PAPP-A with other biochemical markers used for biochemical prenatal screening. Design: Retrospective study. Setting: First Institute of Medical Chemistry and Biochemistry and Institute for Clinical Biochemistry, First Medical Faculty, Charles University. Institute for Care of Mother and Child, Prague. Patients: One hundred forty one pregnant women, who undergo biochemical prenatal screening for chromosomal disorders between 7th and 13th week were studied. In addition six women in the second trimester and five women with twin pregnancies, two cases of trisomy 21 and one case of trisomy 18 in second trimester were available for study. Methods: Maternal serum levels of PAPP-A, human chorionic gonadotropin (hCG) and alfa-1-fetoprotein (AFP) were measured using ELISA methods. A single radial immunodiffusion was used to determine trophoblast-specific-beta-1-glycoprotein (SP1). Results: PAPP-A levels increased throughout the first trimester with median 1,8 mg/l in the 7th week to 23,0 mg/l in the 13th week were studied. In addition six women in the second trimester and five women with twin pregnancies, two cases of trisomy 21 and one case of trisomy 18 in second trimester were available for study. Methods: Maternal serum levels of PAPP-A, human chorionic gonadotropin (hCG) and alfa-1-fetoprotein (AFP) were measured using ELISA methods. A single radial immunodiffusion was used to determine trophoblast-specific-beta-1-glycoprotein (SP1). Results: PAPP-A levels increased throughout the first trimester with median 1,8 mg/l in the 7th week to 23,0 mg/l in the 13th week of pregnancy. PAPP-A serum levels from 3 women with twin pregnancies were higher than in women with singleton pregnancies. Serum levels of PAPP A in two women with fetus affected by chromosomal disorders did not differ from normal pregnancies. Correlation coefficients between PAPP-A and AFP and between PAPP-A and SP1 were statistically significant (r = 0.42, P < 0.001, respectively r = 0.54, P < 0.001). The levels of PAPP-A and HCG did not correlate significantly (r = 0.019, P = 0.82). Conclusion: We established first trimester medians for PAPP-A, which are necessary for evaluation of the pathological values. We found statistically significant correlation betweenPAPP-A and SP1 and PAPP-A and AFP.

        Key words: pregnancy-associated plasma protein A (PAPP-A), human chorionic gonadotropin (HCG), alfa-1-fetoprotein (AFP), trophoblast-specific-beta-1-glycoprotein (SP1), biochemical prenatal screening, first trimester