title: Maternal serum total hCG and free beta-hCG in the first trimester from trisomy 21 pregnancies
authors.affiliation: Endocrine Unit, Clinical Biochemistry Department, Harold Wood Hospital, Gubbins Lane. Romford, RM3 0BE, UK.
authors.initials: K
authors.lastname: Spencer
authors.initials: DA
authors.lastname: Aitken
authors.initials: JA
authors.lastname: Crossley