Antenatal screening

Screening for fetal abnormality is a growth industry. Amniocentesis with karyotyping of fetal cells obtained from amniotic fluid at around 16 weeks' gestation was introduced widely in the mid-1970s and is now universal. The association of Down's syndrome with low concentrations of (alpha) fetoprotein and high concentrations of ß human chorionic gonadotrophin in maternal serum led in June 1993 to a call for providing screening for all who wanted it.3 Soon, however, concern was expressed about inadequate counselling of pregnant women,4 5 who commonly find it difficult to understand the statistical concepts of risk without a great deal of help (many professionals find it difficult, too). Since there is currently no national policy on screening, and no additional funding to pay for the extra counselling or for the scans during the first trimester that are essential to confirm gestational age, it is not surprising that nearly half of all obstetricians in Britain feel that the current service is inadequate.6 This concern is corroborated by objective surveys of the women themselves.7

The introduction of biochemical screening is sometimes accompanied by disillusion at the relatively low sensitivity of the methods, due not just to technical problems but also to the often surprisingly high proportion of women who decline screening …