title: Down's syndrome screening in multiple pregnancies using alpha-fetoprotein and free beta hCG.
abstract: Second-trimester distributions of the free beta human chorionic gonadotrophin (hCG) and alpha-fetoprotein (AFP) levels in 420 twin and 19 triplet pregnancies were measured and compared with the distributions in 6661 singleton pregnancies. On average, the levels of both analytes were twice as high and over three times as high in triplets. Eight sets of twins discordant for Down's syndrome showed elevated levels of free beta hCG and reduced levels of AFP after correction of the multiple of the median for the presence of a twin pregnancy. Screening for Down's syndrome using the twin correction of the multiple of the median is expected to achieve a 51 per cent detection rate at a 5 per cent false-positive rate using these two markers.
authors.affiliation: Clinical Biochemistry Department, Oldchurch Hospital, Romford, Essex, U.K.
authors.forename: K
authors.initials: K
authors.lastname: Spencer
authors.forename: R
authors.initials: R
authors.lastname: Salonen
authors.forename: F
authors.initials: F
authors.lastname: Muller
mesh_terms: D006063:Chorionic Gonadotropin / Q000097:blood*; D018997:Chorionic Gonadotropin, beta Subunit, Human; D004314:Down Syndrome / Q000175:diagnosis / Q000517:prevention & control*; D005189:False Positive Reactions; D005260:Female; D005865:Gestational Age; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D008423:Maternal Age; D010446:Peptide Fragments / Q000097:blood*; D011247:Pregnancy; D011272:Pregnancy, Multiple; D011296:Prenatal Diagnosis; D012016:Reference Values; D014310:Triplets; D014427:Twins; D000509:alpha-Fetoproteins / Q000032:analysis*
chemical_list: D006063:Chorionic Gonadotropin; D018997:Chorionic Gonadotropin, beta Subunit, Human; D010446:Peptide Fragments; D000509:alpha-Fetoproteins