Normal Amniotic Fluid Alpha-fetoprotein Research Articles

Implications of atypical biochemical data in a case of presumed anencephaly

Anomaly scan on a 21 year old primigravida at 22 weeks showed absence of the superior portion of the calvarium with poorly defined cerebral tissue floating in the amniotic fluid. Maternal serum alphafetoprotein (MSAFP) at 18 weeks was 1.4 MOM. The patient was counseled for anencephaly and amniocentesis was performed. Biochemical data consisting of amniotic fluid alphafetoprotein (AFAFP) of 1.94 MOM with weak positive acetylcholinesterase (ACHE) was atypical of classic anencephaly; karyotype was 46, XX. Following termination, fetopsy showed a gaping cranial defect with protruding brain tissue, partially covered by attenuated translucent skin; meninges were torn and congested. Amniotic bands were identified explaining the cranial findings. Radial aplasia and imperforate anus further suggested VATER. While normal MSAFP can be seen with anencephaly, a normal AFAFP and weak positive ACHE are atypical. In the context of the post-mortem findings, it is presumed that without pregnancy termination, expansion of the cranial anomaly would have eventually lead to unequivocally abnormal biochemical results. This case suggests that alternative etiologies, in particular amniotic bands, be considered when atypical biochemical data is seen at midtrimester in the presence of apparent anencephaly.

Amniotic fluid platelet factor 4 and beta-thromboglobulin as markers of structural abnormalities.

Platelet factor 4 (PF4) and beta-thromboglobulin (BTG) are unique markers of irreversible platelet activation. We measured PF4 and BTG in amniotic fluid from 102 genetic amniocenteses, in which 78 had normal amniotic fluid alpha-fetoprotein (AFP) levels with normal pregnancies, and 24 had high amniotic fluid AFP levels with abnormal pregnancies. PF4 and BTG were significantly higher in the abnormal pregnancy/elevated amniotic fluid AFP group (p < 0.002 in each case) and correlated with AFP expressed as multiples of the median (p < 0.05 and p < 0.0001, respectively). Our results are compatible with passage of PF4 and BTG across fetal membranes and/or enhanced fetal platelet activation in fetuses with structural anomalies and elevated AFP.

Prenatal ascertainment of triploidy by maternal serum alpha‐fetoprotein screening

We report our experience in ascertaining fetal triploidy during routine maternal serum alpha-fetoprotein (MSAFP) screening. Three cases were identified after elevated MSAFP tests. Two of the three had normal amniotic fluid alpha-fetoprotein (AFAFP). The third had amniocentesis too late for AFAFP interpretation. Three additional cases were detected by amniocentesis without prior MSAFP screening and none had an elevated AFAFP. A literature review revealed eight triploid fetuses detected as a result of an elevated MSAFP. Of the five with AFAFP quantitation, only one had an abnormal value and the elevation was minimal. In these 14 cases from our own and other reports, ultrasound findings of placental and fetal abnormalities were often noted, but a pattern diagnostic of triploidy was not present. We conclude that, for optimal prenatal detection of triploidy, fetal karyotyping should be included when an amniocentesis is performed for elevated MSAFP.

Amniotic fluid acetylcholinesterase: Implications of an inconclusive result

The implications of an "inconclusive" acetylcholinesterase test (a faint but true band) in amniotic fluid were studied over a 2 1/2-year period in our laboratory. One thousand one hundred fifty-four amniotic fluid samples were tested for acetylcholinesterase and alpha-fetoprotein; the rate of an inconclusive acetylcholinesterase result was 3.3% (38 of 1154). Fourteen such results were found in patients with a high amniotic fluid alpha-fetoprotein level (23.3%), and 24 results were associated with normal amniotic fluid alpha-fetoprotein levels (2.19%). The rates of congenital fetal malformation associated with an inconclusive acetylcholinesterase result in the two groups were 57.14% and 37.5%, respectively. In amniotic fluid samples obtained before 15 weeks' gestation, there was a higher rate of inconclusive acetylcholinesterase tests (9.29%), but a lower percentage of malformed fetuses were found compared with later in pregnancy (2.46% and 56%, respectively). Thus we suggest the terminology "equivocal" for early specimens and "suspicious" for later specimens. If obtained in early second trimester and the ultrasound scan is normal, such findings implicate the need for a careful search for fetal malformations. A positive pregnancy outcome may be expected in most cases.

Prenatal diagnosis of Pena‐Shokeir syndrome type 1

This report describes the sonographic diagnosis of the Pena-Shokeir syndrome type 1 during the second trimester of a pregnancy which was electively terminated. The mother had previously delivered a macerated, hydropic infant with multiple congenital anomalies. The diagnosis was based on the recurrence of hydramnios and nonimmune hydrops in a fetus with normal chromosomes, normal amniotic fluid alpha-fetoprotein, normal fetal echocardiography, and lack of evidence of a lysosomal storage disease. These observations suggest that serial sonography during the second trimester in pregnancies at risk may allow for the prenatal diagnosis of the Pena-Shokeir syndrome type 1. Without further experience, it would not be prudent to suggest to couples at risk that the prenatal diagnosis of a recurrence can be assured with a high degree of accuracy.

Elevated maternal α-fetoprotein levels with subsequent fetal exsanguination

Presented is a case with persistently elevated maternal serum alpha-fetoprotein and normal amniotic fluid alpha-fetoprotein values associated with subsequent fetal-maternal bleeding and fetal death. Fetal-maternal bleeding, with potential for rhesus sensitization and fetal death, should be considered in the presence of elevated serum alpha-fetoprotein levels.

Outcome of pregnancies associated with raised serum and normal amniotic fluid alpha fetoprotein concentrations.

Outcome of pregnancies associated with raised serum and normal amniotic fluid alpha fetoprotein concentrations.