ABSTRACT
Maternal serum alpha-fetoprotein (MSAFP) screening has been widely used and proven valuable in the prediction of a variety of fetal disorders. Any laboratory intending to provide MSAFP screening needs to establish its own reference data. In order to establish a normal MSAFP median value at our own laboratory, 5256 samples of MSAFP were collected from uncomplicated, singleton pregnant women between 13 and 24 weeks' gestation. The MSAFP median levels steadily rise with advancing gestation about 16% per gestational week in average. There were 0.17% and 4.4% of the pregnancies with serum AFP levels less than 0.25 multiple of the median (MoM) and 0.5 MoM respectively, and 4.22% and 1.66% with serum levels above 2.0 MoM and 2.5 MoM. Accurate and satisfactory interpretation of MSAFP screening should be emphasized in the establishment of a well-developed normal median value.
Subject(s)
Pregnancy/blood , alpha-Fetoproteins/metabolism , Female , Humans , Pregnancy Trimester, Second , Reference ValuesABSTRACT
To investigate the association between low amniotic fluid alpha-fetoprotein (AFP) and trisomy pregnancies, we retrospectively reviewed 26 trisomy pregnancies including 18 fetuses with Down's syndrome and eight with trisomy 18. The amniotic fluid AFP median values of Down's syndrome, trisomy 18, and the study groups were 0.73 MoM, 1.15 MoM, and 0.85 MoM, respectively. There was a significant difference between the mean values of the Down's syndrome-affected fetuses (0.78 +/- 0.29 MoM) and that of the control group (p < 0.001), whereas no such difference was found for that of trisomy 18-affected fetuses (1.16 +/- 0.38 MoM). Only three patients in the study group (3/26, 11.5%) had an amniotic fluid AFP value below 0.5 MoM, including the two cases of Down's syndrome (2/18, 11.1%) and one case of trisomy 18 (1/8, 12.5%). Most of the values for the trisomy pregnancies were within the normal range, thereby precluding the possibility of using this measurement as an alternative to fetal karyotyping as a screening test for Down's syndrome or other trisomy pregnancies.
Subject(s)
Amniotic Fluid/chemistry , Chromosomes, Human, Pair 18 , Down Syndrome/diagnosis , Fetal Diseases/diagnosis , Prenatal Diagnosis , Trisomy/diagnosis , alpha-Fetoproteins/analysis , Female , Humans , Pregnancy , Pregnancy Trimester, Second , Retrospective StudiesABSTRACT
To assess the relationship between alpha-fetoprotein (AFP) concentrations of amniotic fluid and maternal serum from 16 to 18 weeks' gestation, 890 paired samples of maternal serum and amniotic fluid were collected from women with normal singleton pregnancies. The gestational age was determined by ultrasonographic dating before amniocentesis, and the AFP measurements were performed by a single reference laboratory. There was a significant rise in the maternal serum AFP (MSAFP) concentration from 16 to 18 weeks' gestation. Amniotic fluid AFP concentrations significantly declined from 16 to 18 weeks' gestation. This study failed to demonstrate any statistical relationship between the AFP concentration of maternal serum and amniotic fluid (r = 0.031). This finding indicates that amniotic fluid AFP levels cannot be predicted by MSAFP levels between 16 and 18 weeks' gestation. Simple diffusion may not be the only mechanism for the transfer of AFP through the fetal membrane to maternal circulation.
