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First trimester urine free beta hCG, beta core, and total oestriol in pregnancies affected by Down's syndrome: implications for first-trimester screening with nuchal translucency and serum free beta hCG.
Spencer K, Noble P, Snijders RJ, Nicolaides KH.
Prenat Diagn 1997;17:525-38. -
Maternal serum inhibin-A and free beta-hCG concentrations in trisomy 21 pregnancies at 10-14 weeks of gestation.
Noble PL, Wallace EM, Snijders RJ, Groome NP, Nicolaides KH.
BJOG 1997;104:367-71.