Maternal serum alpha-fetoprotein screening after chorionic villus sampling

To evaluate whether maternal serum alpha-fetoprotein (MSAFP) concentrations at 15-18 weeks' gestation are influenced by chorionic villus sampling performed three to ten weeks earlier, MSAFP levels were determined for 417 postchorionic villus sampling patients and 967 control subjects without previous chorionic villus sampling. Statistical comparison of the medians, distributions, and proportions above defined multiples of the median demonstrated no significant difference between the two populations. These results indicate that MSAFP screening in postchorionic villus sampling patients should be reliable and that values may be interpreted using criteria similar to those used for the general population.