Safety of handling cytotoxic agents: a cause for concern by pharmaceutical companies?

Maternal serum afetoprotein in multiples of the median FIG 4-Absolute probability of carrying babies with Down's syndrome at maternal serum ct fetoprotein concentrations according to maternal age at expected date of delivery. (*Probability calculated by two previous reports.4 5) With a screening programme to identify a group of mothers at increased risk of a pregnancy with Down's syndrome, it is possible to calculate individual risks or absolute probabilities on which decisions for or against further diagnostic procedures can be based. The absolute probability of an individual woman with known maternal serum a fetoprotein concentration and age at expected date of delivery can be calculated by the method described by Dennis and Carter for overlapping normal distributions.7 Figure 3 shows the probability of a mother carrying a baby with Down's syndrome with maternal serum u fetoprotein concentration between 013 and 1-5 multiples of the median where the probability of carrying a baby with Down's syndrome is one using the distributions shown in table II. Figure 4 shows the absolute probability of carrying a baby with Down's syndrome calculated for individual values of maternal serum (a fetoprotein by maternal age. We therefore suggest that maternal serum a fetoprotein concentration equal to or less than the sliding scale described by Cuckle et al2 should be used as a screening test to identify women whose collective risk of having a baby with Down's syndrome is greater than one in 200, and these will be the women aged 32 and over. The accuracy of the information on the high risk group could then be improved by repeat maternal serum a fetoprotein screening and scan. Their absolute probability of carrying a baby with Down's syndrome could then be calculated using the aforementioned probability at the individual maternal age and an informed decision about further diagnostic tests could be based on a known risk of carrying a baby with Down's syndrome, the views of the parents, and the risks of the procedure. We thank the obstetricians, paediatricians, and district medical officers and the North East Thames Regional Cytogenetic and AFP laboratories for their cooperation and Professor Timothy Chand for his help in collecting MSAFP data. We thank the Royal College of Physicians Research Unit for their help and encouragement and Mrs Joy Robertson for secretarial help.