[Increased AFP in maternal serum as an indication for invasive diagnosis]

The association of increased maternal serum alpha-fetoprotein levels (MS-AFP) with certain morphologic anomalies of the fetus is fully established. These anomalies are abdominal wall defects (e.g. omphalocele, gastroschisis, complete eventration), neural tube defects (anencephalus, spina bifida, encepalocele) and other malformations (e.g. coccygeal teratoma). The present study compares MS-AFP levels with amniotic fluid alpha-fetoprotein (AF-AFP) and acetylcholinesterase activity, the results of ultrasound, genetic and morphologic examination. Between April 1992 and November 1995 60 patients were referred to our clinic for further diagnosis after detection of elevated MS-AFP. After an ultrasound examination was carried out amniocentesis (AC) was performed in 54 cases, AC + placentesis (PC) in 3 patients and PC only in 3 cases with anhydramnion. Mean maternal age was 29 years (range 20-37 years). Punction was performed at a median of 19 + 1 weeks of gestation (15 + 2-23 + 2 weeks of gestation). MS-AFP, AF-AFP and acetylcholinesterase activity was measured. MS-AFP and AF-AFP were given as multiples of the median (MoM). Values < or = 1-2.0 MoM were considered normal. Elevated levels were defined to be greater than 2 MoM. In all cases the chromosomal finding was normal or norm variant. Sonographical anomalies were detected in 7 fetuses (3 cases with spina bifida, 1 case with omphalocele and 3 cases with abdominal wall defects in connection with other malformations). All sonographic diagnoses were confirmed post partum. The MS-AFP varied between 0.9-6.0 MoM. In 7 cases MS-AFP previously (referring center) evaluated as increased was found to be within normal range in our department. This cases included normal values were found in 30 cases and 25 findings were pathological. 2 out of 7 structurally abnormal fetuses had normal values, 5 of them had elevated MS-AFP. In the group of normal fetuses the highest MS-AFP we found was 6.6 MoM. In the AC-group the AF-AFP ranged between 0.7-8.7 MoM, it was within normal range in 50 and pathological in 8 cases. In the group of fetuses without structural anomalies the highest AF-AFP was 7.5 MoM. In the group of fetuses with structural anomalies the AF-AFP values were 1x normal and 3x pathological (> 3.5 MoM). Acetylcholinesterase activity in the amniotic fluid was negative in 51 cases, positive in 4 cases and faint positive in 2 cases. In all fetuses with structural anomalies in which an AC could be performed, acetylcholinesterase activity was positive. On the other hand we found only 1 of the structurally normal fetuses with positive acetylcholinesterase activity. Elevated MS-AFP and AF-AFP may be an indicator for morphological anomalies. Yet there were many positive results without any sonographical findings. The determination of a positive acetylcholinesterase activity in the amniotic fluid is more specific. All malformations have been detected by ultrasound examination before the results of the AF-AFP were available.