Alpha-1-fetoprotein concentration in cord serum as a parameter for gestational age

Alpha 1-fetoprotein (AFP) reference values in infants up to 2 years of age

The aim of this study was to establish reference values and factors associated with serum AFP elevation in infants. Five hundred twenty-four samples collected from infants up to the age of 2 years at the University Hospital Düsseldorf (Germany) were analyzed. At birth mean serum AFP levels were 41,687 ng/ml in 256 term babies and 158,125 ng/ml in 90 premature babies born before the 37th gestational week, excluding samples from children with factors known to be associated with AFP elevation. In the first 4 weeks of life, AFP levels decreased by 50% in 5.1 days in term babies. Between day 180 and 720 of life, AFP levels up to 87 ng/ml were within the 95.5% interval (assumed logarithmic normal distribution) with a mean of 8 ng/ml without a further decline. By the age of 2 years the infants of this study had not reached adult serum AFP levels (0-6 ng/ml).

[Experiments on the induction of embryopathies and changes in alpha-foetoprotein and serum albumin concentrations in the chick embryo]

Administration of 3 microg dexamethasone at day 8 of incubation into the allantoic cavity resulted in various embryopathies in embryos by the 15th day of incubation. Chicken alpha-foetoprotein (chAFP) and serum albumin concentrations, when examined at the 12th day of incubation, were below the corresponding controls (P<0.01), whereas total serum protein was only slightly lower, On day 15 chAFP concentrations were similar to those of the controls, serum albumin values were markedly reduced and total serum protein was significantly decreased. The results suggested a selective reduction of serum albumin synthesis in the 15-day-old chick embryo. Following administration of 2 IU insulin on the first day of incubation, into the yolk sac, one third of the embryos developed embryopathies. ChAFP, serum albumin and whole serum protein values were unchanged on either the 12th day or 15th day of incubation. Inoculation of 100 microg adrenaline into the allantoic cavity on the sixth day of incubation resulted in embryopathies in only a few instances. ChAFP total serum protein values were not affected. However, serum albumin concentrations were significantly lower on the 12th day, but not on the 15th. The responses to L-thyroxine were both time- and dose-dependent. Inoculation of 2 microg thyroxine on the second day of incubation resulted in few embryopathies. ChAFP levels were significantly lower on the 12th and 15th day of incubation. In contrast, serum albumin and total serum protein concentrations were normal at both times. Similar results were obtained when 2 microg of thyroxine were administered at the third day of incubation. Thus in order to inhibit selectively chAFP synthesis, administration of 2 microg thyroxine on day 2 or 3 of incubation is suggested. When 10 microg thyroxine were injected on day 8 of incubation, 80% of the embryos showed embryopathies on day 12 of incubation. ChAFP and serum albumin levels were markedly depressed. The concentration of total serum protein was significantly decreased on day 12 but less so, though still significantly, on day 15. These results demonstrate the possibility to influence selectively chAFP and serum albumin synthesis, thereby facilitating studies on chemically induced teratological, including pathophysiological, processes in the avian embryo.

Serum alpha-fetoprotein--a biochemical indicator of prenatal hypothyroidism

Serum alpha-fetoprotein (AFP) was analysed at 10-30 days of age in infants with positive TSH screening tests for congenital hypothyroidism. These levels were significantly higher in infants with true positive screening tests than in those with false positive tests; 27 of 43 infants with congenital hypothyroidism had serum AFP levels above the age-related reference range. The postnatal rate of elimination of AFP from serum did not differ in hypothyroid and euthyroid infants, indicating that the difference in serum AFP was due to more extensive synthesis in hypothyroid individuals. The level of serum AFP was inversely correlated with the roentgenological skeletal maturation index. It is postulated that increased serum AFP is caused by prenatal hypothyroidism and that analysis of serum AFP is a valuable tool to identify those infants with congenital hypothyroidism who are at risk of neuropsychological sequelae.

Strain and sex differences in serum alpha-fetoprotein levels in Mus musculus

Normal levels of circulating serum alpha-fetoprotein (AFP) in different inbred strains of mice, as determined by radioimmunoassay, are reported. These strains show different and characteristic values for the mean serum AFP concentration, suggesting genetic control of the serum level of this protein. Furthermore, within each strain a difference in serum levels of the protein is observed between sexes; males have a significantly higher serum AFP concentration.

Alpha-fetoprotein: a review

Alpha fetoprotein (AFP) is the major protein of fetal serum and most resembles albumen, which replaces it shortly after birth. It is produced by fetal liver and passes into the amniotic fluid (AF) via fetal urine. A small amount crosses the membranes into the maternal circulation. Excluding fetal blood contamination, elevated AF/AFP levels indicate fetal demise or one of several abnormalities. Maternal serum (MS) AFP measurement can be used as a screening procedure to identify neural tube defects providing a rigorous protocol is followed. This requires that a laboratory establish its normal range of MS/AFP levels between 15 and 20 weeks gestation, employ a reliable assay with adequate controls, and has recourse to genetic counseling as well as expert sonography, amniocentesis and amniography if necessary. Pregnancy is the only normal situation in which AFP is present after birth. It may be present in high levels in certain malignancies and has been useful in monitoring their recurrence. This article will review the history, biochemistry, and different assays of AFP in AF and blood as well as the indications and limitations for their use.

Endogenous clearance rate and synthesis of alphafoetoprotein during and after blood exchange transfusion in hyperbilirubinaemic newborns

Plasma alphafoetoprotein (AFP) concentration was monitored in 22 hyperbilirubinaemic infants during blood exchange transfusion at the age of 0-4 days, in order to determine the endogenous clearance rate and demonstrate possible postnatal synthesis of AFP. The rapid fall in plasma AFP during the transfusion to 19 +/- 4% (mean +/- S.D.) was followed by an increase to 81 +/- 15% of the initial concentration; only a 68% rise was expected after the establishment of a new equilibrium between the intra- and extravascular pools of AFP. Repeated transfusion in the same individuals gave similar findings. In two infants the total amount of AFP in these pools increased by 4.0-7.4 mg after the transfusions. The results could be accounted for by postnatal AFP synthesis. Because of the diffusion of AFP from the extravascular compartment to the intravascular pool the actual turnover rate of AFP could not be measured. The estimated magnitude of endogenous turnover rate of AFP, 0.02-0.09 min-1, gave a mean half-life of about 20 min, which is distinctly shorter than that of AFP in plasma (3-5 days); this could be due to either continuous synthesis of AFP or transfer of presynthesized AFP from the liver cells to extracellular pool. We postulate that either the synthesis or the turnover rate of AFP is controlled by the plasma AFP concentration via a negative feedback mechanism.

Serum alpha-fetoprotein in adults, in women during pregnancy, in children at birth, and during the first week of life: a sex difference

In order to investigate whether a sex difference exists in alpha-fetoprotein serum concentration, blood samples were collected from 133 adult men, 52 adult women, 239 pregnant women at different ages of gestation, 16 girls and 18 boys at birth, and seven girls and seven boys during the first week of life. In the case of 15 boys and 10 girls, blood samples were also collected from their mothers at the time of delivery. Serum AFP was measured by a radioimmunoassay method. In all neonates the mean value was 625 times higher than in all mothers at the time of delivery and 13,000 times higher than in adults. No difference was found between mothers of girls and those of boys both during pregnancy and at the time of delivery. However, at birth, the fetal AFP serum concentration was 1.8 (p less than 0.001) times higher in boys than in girls. This sex difference was maintained during the first week of life. The half-life of serum AFP was 5 to 6 days in the neonate. The origin and the possible physiologic significance of such sex difference in AFP deserve further investigations.

[Variations of the concentrations of certain glycoproteins in maternal serum, fetal serum and amniotic fluid during pregnancy (author's transl)]

The authors investigated systematically the variations during normal pregnancies of the concentrations of alpha-1-antitrypsin, orosomucoid, transferrin and alpha-fetoprotein simultaneously in maternal serum, fetal serum and amniotic fluid. The role of certain factors such as the gestational age birth weight, placental weight and pairty were studied with regard to variations in the concentrations of each of these proteins. This research permitted the definition during pregnancy of the normal concentrations for these four proteins and allowed us to learn more about protein exchanges between fetal blood, maternal blood and amniotic fluid. There exists a difference between the concentrations of alpha-1-antitrypsin and of orosomucoid found for primigravidae and for multigravidae. The role of these glycoproteins in preventing the mother from rejecting the fetus (insofar as the fetus may be considered as an allograft) is discussed.

Studies on maturity in newborn infants. VIII. Alpha-foetoprotein and albumin

Cord blood of 125 newborn infants of various gestational ages has been analysed for the amounts of alpha-foetoprotein and albumin using an electroimmunoassay. The quotient alpha-foetoprotein/birth weight was recorded as well. All the three measureements correlate fairly well with the gestational age of newborn infants. Measuring alpha-foetoprotein is not of the same value, however, in estimating gestational age as is the simple scoring of external characteristics.

[Carcinofetal antigens. I. alpha-fetoprotein (author's transl)]

Alpha-fetoprotein (AFP) is an alpha1-glycoprotein (M.W. about 65000) appearing in the fetal serum of most mammals including man during the early stages of pregnancy; 4 weeks after birth it disappears altogether or exists at very low concentrations as in the normal adult. AFP is formed in the yolk sac, the fetal liver and the gastro-intestinal tract. One of its physiological functions in fetal life is supposed to be the protection of the fetus from maternal oestrogens (oestrophilic property). The clinical significance of AFP is based on the regular and increasing production in primary liver cell carcinoma, less frequently in teratogenetic tumors where it serves as a control of therapy and course of the disease. Less frequent, minor and temporary increases in the AFP serum level occur in several primary tumors with secondary liver involvement, and in inflammatory gastro-intestinal diseases, e.g. of the liver (hepatitis, cirrhosis). AFP has an increasing importance in gynecology (gestational age, fetal distress syndrom, malformations, hydatidiform mole/chorion carcinoma). The physico-chemical properties of AFP are widely known. Both fetal and tumor AFP appear to be immunologically and biochemically identical, as are that of tissue and biological fluids. The differences observed (variants, microheterogeneity) depend mainly on the different content of sialic acid. An antigenetic relationship exists, between the AFP of most species. The immunodiffusion (Ouchterlony) is the most frequently used but relatively insensitive test (1-5 mug/ml) in finding AFP, whereas the radioimmunoassay is the most sensitive one (up to 0,25 ng/ml) and permits the determination of normal serum levels in adults (below 20 ng/ml). The serum concentration in healthy pregnant women lies up to 500 ng/ml, in patients with hepatitis, liver cirrhosis and other liver diseases mostly under 3 mug/ml, whereas in those with primary liver cell carcinoma levels up to and above 600 mg-percent have been found.

[Variations of human serum alpha-fetoprotein concentration after partial hepatectomy (author's transl)]

Alpha-fetoprotein serum concentrations were determined by radioimmunoassay in 5 patients with echinococcus involvement of the liver. In 4 cases a partial hepatectomy was possible, whereas in 1 case laparotomy had to be confined to an exposure of the liver hilus because of too many dispersed echinococcus cysts. All patients showed normal AFP levels below 20ng/ml before operation. Within the first to third postoperative day maximal AFP increases of AFP level between 2760 and 5600 ng/ml developed, which returned to normal during the following days and weeks. One patient who was submitted to strumectomy and to the same anaesthetic liver charge had no change in her normal AFP concentration. The postoperative changes of AFP level observed are interpreted as an expression of a quick and intense liver cell regeneration following the surgical treatment.