In the context of a prospective study on the adverse effects of anti-epileptic drugs on fetal outcome, we evaluated our experience with prenatal diagnosis by ultrasonography and alpha-fetoprotein (AFP) determination in amniotic fluid. We compared these results with AFP values in maternal serum obtained prior to amniocentesis. From November 1985 to July 1990, amniocentesis at 16-18 weeks of gestation was performed in 267 pregnancies of 237 different women using anti-epileptic drugs. Among 92 pregnancies with maternal valproic acid use, five (including one concordantly affected monozygotic twin-pair) were terminated because of a spina bifida aperta, all prenatally diagnosed by AFP determination and acetylcholinesterase electrophoresis in amniotic fluid. The maternal serum AFP level was raised (> or = 2.5 multiples of the median (MOM) for singleton pregnancies and > or = 4.5 MOM for twin pregnancies) in only two of these five affected pregnancies. We emphasize that maternal serum AFP levels may be unreliable for prenatal screening for fetal neural tube defects in women taking valproate and recommend that amniocentesis and fetal ultrasound examination should be offered directly.

In women at low risk, elevated MSAFP and/or maternal serum hCG values are predictive of adverse pregnancy outcome. In women with a priori elevated risk, abnormal serum values do not increase this risk.

Investigations were performed to avoid cross‐reactions in the enzyme linked immunosorbent assay, using the sandwich technique, for detection of Staphylococcus aureus enterotoxin type B. Non‐specific reactions can be caused by cross‐reacting antigens and by Protein A, produced by S. aureus. The former reactions can be prevented by adsorption with culture filtrate of non‐toxin type B producing strains. The latter reaction is caused by the binding of Protein A to the Fc fragments of the IgG antibodies. Interference by Protein A was completely eliminated by using the F(ab')2 fragments of the IgG antibodies. ELISA experiments in which these purified F(ab')2 fragments were used resulted in a highly specific detection of entertoxin type B, both in culture filtrates and in foods.