Early termination of anencephalic pregnancy after detection by raised alpha-fetoprotein levels

Identification of PCSK9 as a novel serum biomarker for the prenatal diagnosis of neural tube defects using iTRAQ quantitative proteomics

To identify candidate serum molecule biomarkers for the non-invasive early prenatal diagnosis of neural tube defects (NTDs), we employed an iTRAQ-based quantitative proteomic approach to analyze the proteomic changes in serum samples from embryonic day (E) 11 and E13 pregnant rats with spina bifida aperta (SBA) induced by all-trans retinoic acid. Among the 390 proteins identified, 40 proteins at E11 and 26 proteins at E13 displayed significant differential expression in the SBA groups. We confirmed 5 candidate proteins by ELISA. We observed the space-time expression changes of proprotein convertase subtilisin/kexin type 9 (PCSK9) at different stages of fetal development, including a marked decrease in the sera of NTD pregnancies and gradual increase in the sera of normal pregnancies with embryonic development. PCSK9 demonstrated the diagnostic efficacy of potential NTD biomarkers [with an area under the receiver operating characteristic curve of 0.763, 95% CI: 065-0.88]. Additionally, PCSK9 expression in the spinal cords and placentas of SBA rat fetuses was markedly decreased. PCSK9 could serve as a novel molecular biomarker for the non-invasive prenatal screening of NTDs and may be involved in the pathogenesis of NTDs at critical periods of fetal development.

Spina bifida

Spina bifida is a birth defect in which the vertebral column is open, often with spinal cord involvement. The most clinically significant subtype is myelomeningocele (open spina bifida), which is a condition characterized by failure of the lumbosacral spinal neural tube to close during embryonic development. The exposed neural tissue degenerates in utero, resulting in neurological deficit that varies with the level of the lesion. Occurring in approximately 1 per 1,000 births worldwide, myelomeningocele is one of the most common congenital malformations, but its cause is largely unknown. The genetic component is estimated at 60-70%, but few causative genes have been identified to date, despite much information from mouse models. Non-genetic maternal risk factors include reduced folate intake, anticonvulsant therapy, diabetes mellitus and obesity. Primary prevention by periconceptional supplementation with folic acid has been demonstrated in clinical trials, leading to food fortification programmes in many countries. Prenatal diagnosis is achieved by ultrasonography, enabling women to seek termination of pregnancy. Individuals who survive to birth have their lesions closed surgically, with subsequent management of associated defects, including the Chiari II brain malformation, hydrocephalus, and urological and orthopaedic sequelae. Fetal surgical repair of myelomeningocele has been associated with improved early neurological outcome compared with postnatal operation. Myelomeningocele affects quality of life during childhood, adolescence and adulthood, posing a challenge for individuals, families and society as a whole. For an illustrated summary of this Primer, visit: http://go.nature.com/fK9XNa.

Neural tube defects: recent advances, unsolved questions, and controversies

Neural tube defects are severe congenital malformations affecting around one in every 1000 pregnancies. An innovation in clinical management has come from the finding that closure of open spina bifida lesions in utero can diminish neurological dysfunction in children. Primary prevention with folic acid has been enhanced through introduction of mandatory food fortification in some countries, although not yet in the UK. Genetic predisposition accounts for most of the risk of neural tube defects, and genes that regulate folate one-carbon metabolism and planar cell polarity have been strongly implicated. The sequence of human neural tube closure events remains controversial, but studies of mouse models of neural tube defects show that anencephaly, open spina bifida, and craniorachischisis result from failure of primary neurulation, whereas skin-covered spinal dysraphism results from defective secondary neurulation. Other malformations, such as encephalocele, are likely to be postneurulation disorders.

Uterine malformation: a cause of elevated maternal serum alpha-fetoprotein concentrations

This study was undertaken to investigate the association between uterine anomalies and unexplained elevated maternal serum alpha-fetoprotein (MSAFP) concentrations during the early second trimester. The incidence of uterine anomalies was retrospectively evaluated among pregnant women showing elevated (> 2.5 multiples of the median) mid-trimester maternal serum AFP (N = 312) concentrations in otherwise normal singleton pregnancies and then compared with that amongst patients from the same clinic showing normal serum AFP results (N = 28410). Basic clinical data of the study group were also analysed. The rate of diagnosed developmental uterine malformations in patients showing elevated MSAFP levels was 1 in 31, whereas the rate in the control group was 1 in 710 (3.2 per cent vs. 0.14 per cent). The relative risk was 22.1 [95 per cent confidence interval (CI) 11.1-43.7]. Amniotic fluid (AF) concentrations of AFP were normal in the study group. Our preliminary observations suggest that elevated MSAFP in the second trimester may in some cases be explained as being solely a result of uterine anomaly. The fetal to maternal transfer of AFP occurs by a transplacental, not a transamniotic, route, since AFAFP concentrations were normal. Consequently, obstetricians taking care of these patients should take this possibility into account.

Unexplained elevated maternal serum alpha-fetoprotein levels and perinatal outcome in an urban clinic population

OBJECTIVE

Our purpose was to determine whether obstetric patients with unexplained elevated maternal serum alpha-fetoprotein levels from an indigent clinic population are at increased risk for adverse perinatal outcome compared with similar patients with normal values.

STUDY DESIGN

Perinatal outcomes from inner-city obstetric patients with unexplained elevated maternal serum alpha-fetoprotein levels (> 2.0 multiples of the median) were compared with patients from the same clinic with normal values. The frequency of adverse outcomes in the two groups was subjected to chi 2 analysis.

RESULTS

Adverse perinatal outcomes occurred in 33 of 57 (58%) of the subjects with unexplained elevated maternal serum alpha-fetoprotein levels compared with 163 of 719 (23%) patients with normal values (p < 0.001). Statistically significant differences were observed for abruptio placentae (p < 0.025), intrauterine growth retardation (p < 0.025), stillbirth at > 20 weeks (p < 0.001), and pregnancy-induced hypertension (p < 0.01). Differences in the frequencies of preterm premature rupture of membranes, preterm delivery, pregnancy loss < 20 weeks, and congenital malformations were not statistically significant.

CONCLUSION

In contrast to a previous report, we found that unexplained elevated maternal serum alpha-fetoprotein levels confer an increased risk of adverse perinatal outcome in an urban clinic population over and above the already increased risk related to socioeconomic status.

alpha-Fetoprotein values in monkey (Macaca mulatta) pregnancy

The pregnant rhesus monkey's (Macaca mulatta) potential as a model for understanding the dynamics of alpha-fetoprotein (AFP) metabolism in human pregnancy was evaluated. AFP levels in maternal and fetal serum and amniotic fluid were determined by radioimmunoassay. Significant correlations were found between decreasing maternal serum, fetal serum and amniotic fluid AFP concentrations and increasing gestational age. However, these data are not consistent with the AFP changes reported in human pregnancy. It appears that this animal has limited applicability as a model in this aspect of human pregnancy.

Amniotic fluid levels of fibrin(ogen) degradation fragment E and alpha-fetoprotein in normal pregnancy and with fetal neural tube defect

Amniotic fluid levels of alpha-fetoprotein (AFP) and fibrin(ogen) degradation fragment E (FgE) were measured in 214 normal subjects and 27 pregnancies associated with an abnormal fetus (open neural tube defect or exomphalos). AFP levels showed no overlap between the normal and abnormal groups, thus confirming the reliability of the AFP assay in the detection of these abnormalities. FgE levels however showed considerable overlap and could not be used as a diagnostic parameter. Agarose gel chromatography of the amniotic fluid revealed the presence of large molecular weight FgE related antigen in open neural tube defect suggesting that leakage of proteins from exposed capillaries is responsible for the elevation of amniotic fluid protein levels.

Alpha-fetoprotein

Despite all the information about AFP presented, a great deal still needs to be discovered especially in pregnancy. Geographical and racial differences remain to be elucidated. Similarly, differences in obstetric population in Helsinki and Baltimore, for example, are only now being studied. Sex differences may exist; Lardinois and associates195 cited a higher level of AFP in male than female fetuses. The important questions that need to be answered are whether AFP assays can help improve the other half of prenatal care- that directed to the fetus- and whether the AFP model can help enhance our understanding of the similarities and differences of fetal and cancer cells.

Prenatal detection of anencephaly

Fetal anomalies were suspected clinically in 3 patients, during the second trimester of pregnancy, due to advanced maternal age, hydramnios and abnormal vaginal bleeding respectively. Sonography revealed anencephaly in all of them, confirmed by roentgenograms and also by high amniotic fluid leveal alpha-fetoprotein in 1 of them. The antenatal diagnosis was confirmed in the 3 abortuses. Early screening of all pregnancies at risk for neural tube malformations is strongly recommended.

Raised alpha-fetoprotein levels in amniotic fluid and maternal serum in a triplet pregnancy in which one fetus had an omphalocoele

During the second pregnancy of a 31-year-old patient, who already had a child with hydrocephalus, the ultrasonic scan at 16 weeks gestation demonstrated the possiblity of triplets. Raised amniotic fluid and maternal serum alpha-fetoprotein concentrations were observed at 16 and 17 weeks gestation. The pregnancy was terminated at 17 weeks gestation and one of the fetuses had an extensive omphalocoele, radial aplasia and digital abnormalities.

Pleomorphic virus-like particles in human faeces

Pleomorphic fringed particles bearing some resemblance to orthomyxoviruses and coronaviruses were seen in 90 percent of stools from south Indian children and adults but not in stools from neonates. This finding may be related to the abnormalities of intestinal structure and function common in this region of India.

Immunoglobulin M in human amniotic fluid and its possible association with neural-tube malformations

Immunoglobulin M (IgM) was found in the amniotic fluid from two fetuses with neural tube defects but no in that from normal fetuses. The possible associations of IgM with abnormalities of the central nervous system are discussed.

Alpha-fetoprotein in antenatal diagnosis of congenital nephrosis

Alpha-fetoprotein (A.F.P,) levels were found to ge significantly raised in maternal serum and amniotic-fluid samples form the 16th and 18th weeks of gestation in a woman with an apparently normal fetus but with histological evidence of congenital nephrosis of the Finnish type. Increased concentrations of A.F.P. in early pregnancy with a living fetus are therefore not specific for neural-tube defects; More likely they result from the fetal circulation. Extended investigations, including kidney morphology, should be done in cases of apparent false-positive A.F.P. tests.

[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.

The present status of prenatal detection of neural tube defects

In experimentally induced myelocele in rats, efforts to find neural cells in amniotic fluid (AF) were unsuccessful. Creatine phosphokinase (CPK) and aldolase concentrations studied in serum of 118 and cerebrospinal fluid (CSF) in 9 patients with myelomeningocele showed serum CPK to be significantly elevated and more responsive to additional muscle injury than aldolase, but both enzymes appeared in lower concentrations in patients with myelomeningocele than those with infantile atrophy or cerebral palsy. In CSF, CPK, and aldolase concentrations averaged 4.2 I.U. and 2.7 S.L.U. per milliliter, respectively. Significant CPK elevation (p less than 0.001) was also found in AF from myeloschitic fetuses and maternal rat serum. Although these findings suggest that increased CPK concentration is an indicator of myelocele in rats, the technique is impractical for prenatal detection of human fetus occurs too late in gestation. This does not, however, preclude the value of CPK for detecting onset of paraparesis. In all myeloschitic human fetuses, the CSF communicates directly with AF for at least 3 to 4 weeks. This implies that CSF is probably the principal source of increased alpha-fetoprotein concentration encountered in AF of all pregnancies with NTD. When biological variables are recognized, it is evident that increased concentration of amniotic fluid alpha fetoprotein is a reliable indicator of fetuses with open myelocele and/or anenciphalus.

Alpha fetoprotein levels in maternal serum and in amniotic fluid from early normal pregnancies

Alpha fetoprotein (AFP) was determined in serum from 241 women in the 8th to 43rd week of gestation by quantitative radioimmunoelectrophoresis, and in 103 amniotic fluid samples from the first half of pregnancy by rocket immunoelectrophoresis. Both serum and amniotic fluid samples were obtained from a larger material, but samples were included only from pregnant women whose infants were normal at birth. The 90% normal AFP range was calculated both for maternal serum and for amniotic fluid.

Amniotic fluid alphafetoprotein measurements in the early prenatal diagnosis of central nervous system disorders

Amniotic fluid alphafetoprotein (AFP) has been measured in 520 pregnancies between 8 and 24 weeks of gestation. The normal range of values has been defined for fortnightly periods between these limits. Grossly elevated AFP concentrations were found in four pregnancies leading to spina bifida and nine pregnancies leading to anencephaly. Slightly elevated AFP concentrations were found in one twin pregnancy and two pregnancies affected by rhesus isoimmunisation. Normal AFP values were observed in 36 amniotic fluids from pregnancies where the outcome was rhesus isoimmunisation, an inborn error of metabolism, a cytogenetic disorder or a birth defect unrelated to the central nervous system. The reliability of amniotic fluid AFP in the early prenatal diagnosis of spina bifida and anencephaly and the possibility of performing assays on samples sent by post from any part of the world are emphasized.

Alpha-fetoprotein levels in amniotic fluids from spontaneous abortions

Alpha-fetoprotein (A.F.P.) levels in the amniotic fluid were determined in 54 cases of spontaneous abortion in which the amniotic sac remained intact. These levels were correlated with the morphological and cytogenetic status of the fetus. Of the 29 fetuses with no apparent abnormality 22 had A.F.P. levels below 50 mug/ml, while 10 of the 11 fetuses with severe neural tube defects had raised levels (50-305 mu/ml). Seventeen fetuses had chromosome anomalies of various types. Three out of four which were 45, X had considerably raised A.F.P. levels (78-210 mug/ml) but fetuses with other chromosome constitutions and no neural tube defects had levels no higher than 32 mug/ml.