Changes in circulating alphafetoprotein and human chorionic gonadotrophin following chorionic villus sampling

Chorionic villus sampling (CVS) is rapidly becoming established as a routine procedure for first-trimester fetal diagnosis. The technique can result in fetomaternal haemorrhage and this might sensitize Rhesus-negative mothers and on occasion lead to spontaneous abortion. Serial sampling indicates that there is a rapid rise in alphafetoprotein (AFP) levels following CVS; however, this is not reflected by raised levels at 16-18 weeks and does not influence the subsequent pregnancy outcome. Unlike AFP, alterations in hCG levels are small and variable. Anti-D prophylaxis for non-sensitized Rhesus negative mothers should be given after CVS and the procedure may be contra-indicated in patients who are already sensitized.