The study examines the effectiveness of maternal serum screening for Down's syndrome in early pregnancy. It finds that measuring human chorionic gonadotrophin (hCG) concentrations in maternal serum during the second trimester is an effective screening test, with a lower false positive rate (3%) and higher detection rate (30%) compared to existing tests like unconjugated oestriol (7%) and α-fetoprotein (11%). Combining hCG with other variables further reduces the false positive rate to 0.5% at the same detection rate. This method could detect over 60% of affected pregnancies, more than double the current rate, potentially reducing the number of children born with Down's syndrome in the UK from 900 to 350 annually. The study highlights that maternal age is a poor basis for screening, as it only detects about 30% of Down's syndrome pregnancies. Adding serum tests like hCG and unconjugated oestriol increases detection to 45%. The study also shows that combining multiple tests improves accuracy, with the best results achieved by using all three tests (hCG, α-fetoprotein, and unconjugated oestriol) along with maternal age. This combination allows for a 60% detection rate with a 5% false positive rate. The study also discusses the importance of considering correlations between variables when combining tests. While hCG and maternal age are not correlated, hCG and unconjugated oestriol show a small negative association. The study concludes that maternal age should no longer be the primary screening variable, as it is just one of several that need to be used in combination. The effectiveness of maternal serum screening for Down's syndrome using maternal age and simple blood tests is now possible, allowing for the identification of about 60% of affected pregnancies within a group of about 5% of all pregnancies. This approach could reduce the number of babies born with Down's syndrome in the UK from about 900 a year to about 350. The study also notes that the results are subject to estimation errors and that further studies would likely confirm the reliability of the estimates.The study examines the effectiveness of maternal serum screening for Down's syndrome in early pregnancy. It finds that measuring human chorionic gonadotrophin (hCG) concentrations in maternal serum during the second trimester is an effective screening test, with a lower false positive rate (3%) and higher detection rate (30%) compared to existing tests like unconjugated oestriol (7%) and α-fetoprotein (11%). Combining hCG with other variables further reduces the false positive rate to 0.5% at the same detection rate. This method could detect over 60% of affected pregnancies, more than double the current rate, potentially reducing the number of children born with Down's syndrome in the UK from 900 to 350 annually. The study highlights that maternal age is a poor basis for screening, as it only detects about 30% of Down's syndrome pregnancies. Adding serum tests like hCG and unconjugated oestriol increases detection to 45%. The study also shows that combining multiple tests improves accuracy, with the best results achieved by using all three tests (hCG, α-fetoprotein, and unconjugated oestriol) along with maternal age. This combination allows for a 60% detection rate with a 5% false positive rate. The study also discusses the importance of considering correlations between variables when combining tests. While hCG and maternal age are not correlated, hCG and unconjugated oestriol show a small negative association. The study concludes that maternal age should no longer be the primary screening variable, as it is just one of several that need to be used in combination. The effectiveness of maternal serum screening for Down's syndrome using maternal age and simple blood tests is now possible, allowing for the identification of about 60% of affected pregnancies within a group of about 5% of all pregnancies. This approach could reduce the number of babies born with Down's syndrome in the UK from about 900 a year to about 350. The study also notes that the results are subject to estimation errors and that further studies would likely confirm the reliability of the estimates.