Effect of chorionic villus sampling on serum alpha fetoprotein levels.

Chorionic villus sampling (CVS) is a recent advance in prenatal diagnosis in the first trimester. maternal serum alpha fetoprotein (AFP) screening for neural tube defects is done from 14-17 weeks gestation. Previous studies have shown an elevation of AFP levels following amniocentesis. The aim of this study was to determine the effect of CVS on AFP levels immediately following this procedure. CVS was performed under sonographic guidance on 22 patients between 6 and 12 weeks gestation undergoing elective termination of pregnancy. A Portex catheter was used for obtaining villi. Maternal serum AFP levels were ascertained before and after CVS by radioimmunoassay. In the group of patients 8 weeks or less, no change in AFP levels was seen; in patients greater than 8 weeks gestation, a significant rise in post-biopsy AFP level was noted in 7 of 14 patients. Further studies are planned to clarify the effect of CVS on AFP levels in patients with ongoing pregnancies. Clarification of this issue is important to the role of CVS in prenatal screening.