The work of Bernard et al on combined screening for open spina bifida at 11-13 weeks using biparietal diameter and maternal serum markers has shown that in the first trimester, maternal serum α-fetoprotein (AFP) levels were marginally raised with a median multiple of the median (MoM) of 1.20 from approximately 44 cases. The data are in contrast to a recent publication from Bredaki et al in which data from 14 open spina bifida cases showed a median MoM AFP of 1.75. We find the results from the study by Bernard et al gratifying in that it confirmed earlier studies from my collaborators, which were not referenced in this paper.

Aitken et al showed in 1993 that in 12 cases of open spina bifida, the median MoM AFP was 1.05 in samples collected in the first trimester, but when these same cases were measured in second-trimester samples, the median MoM AFP was 4.38. In a further study with 2 cases of open spina bifida, the AFP MoMs were 0.24 and 0.90. These collective 14 additional cases with an overall median MoM of 0.98 counterbalance the 1.75 found in the 14 cases from Bredaki et al. As confirmed by Bernard et al, maternal serum AFP in the 11-13 week period is a very poor marker of open spina bifida.

Although from these 2 additional studies we had no data on maternal serum-free β-human chorionic gonadotropin (hCG), we did have data on intact hCG in the study by Aitken et al. We found an intact hCG median MoM of 0.99 in the first trimester, which was the same in the second-trimester samples in these cases. There is therefore little evidence to support the use of these biochemical markers in the first trimester in screening for open spina bifida and certainly cannot compete with established ultrasound measures such as the fruit signs, assessment of intracranial translucency, or evidence of reduced biparietal diameter.