OBJECTIVE To establish an algorithm for first-trimester combined screening for trisomy 21 with biochemical testing from 7 to 14 weeks' gestation and ultrasound testing at 11-13 weeks. METHODS This was a multicenter study of 886 pregnancies with trisomy 21 and 222 475 unaffected pregnancies with measurements of free β-human chorionic gonadotropin (β-hCG) and pregnancy-associated plasma protein...

OBJECTIVE To determine the reproducibility of diagnosing tricuspid regurgitation (TR) at 11 + 0 to 13 + 6 weeks' gestation, to examine further the relationship between TR and the presence of chromosomal defects and to calculate the likelihood ratios for trisomy 21 and trisomy 18 in fetuses with TR. METHODS Pulsed wave Doppler of flow across the tricuspid valve was carried out by 12 obstetrici...

Down syndrome (DS) is a birth defect with huge medical and social costs, caused by trisomy of whole or part of chromosome 21. It is the most prevalent genetic disease worldwide and the common genetic cause of intellectual disabilities appearing in about 1 in 400-1500 newborns. Although the syndrome had been described thousands of years before, it was named after John Langdon Down who described ...

INTRODUCTION Free trisomy 21 is responsible for 95% of Down syndrome cases. Advanced maternal age and susceptible recombination patterns are recognized risk factors associated to Down syndrome. Maternal origin of trisomy occurs in approximately 90% of cases; paternal and mitotic origin share the remaining 10%. However, the recombination events that serve as a risk factors for trisomy 21 have no...

OBJECTIVE To investigate the potential value of adding maternal serum alpha-fetoprotein (AFP) to free β-human chorionic gonadotropin (β-hCG) and PAPP-A and fetal nuchal translucency (NT) thickness in first-trimester screening for trisomy 21. METHODS In this case control study, serum AFP was measured in 100 trisomy 21 and 1,500 euploid pregnancies in which screening for trisomy 21 had been per...

OBJECTIVE To determine possible differences in hepatic artery flow between trisomy 21 and euploid fetuses at 11-13 weeks' gestation. METHODS Hepatic artery pulsatility index (PI) and peak systolic velocity (PSV) were measured in fetuses at low risk of aneuploidies (n = 350) and another group at high risk, including 283 euploid and 47 with trisomy 21. The association of hepatic artery PI and P...

A patient with Down's syndrome was found to have 47,XX,+18/47,XX,+21 mosaicism. Chromosome 18 trisomy was found only in 18% of lymphocytes and not in skin fibroblasts. A likely interpretation is double nondisjunction in a single lymphocyte precursor of a trisomy 21 embryo. A brief review of other cases of mitotic multiple nondisjunction and double aneuploid mosiacism is presented.

BACKGROUND Screening for fetal chromosome abnormalities in the first trimester includes analysis of the serological markers pregnancy-associated plasma protein A (PAPP-A) and free beta human choriogonadotropin (free beta hCG). The blood sample is traditionally taken around week 12 of gestation, but the performance of earlier blood sampling is not well documented. METHODS We studied 44,537 sin...

We describe a trisomy 21 with a small supernumerary marker chromosome (sSMC) derived from chromosomes 13/21 and 18 in which the karyotype was 48,XY,+der(13 or 21)t(13 or 21;18)(13 or 21pter→13q11 or 21q11.1::18p 11.21→18pter),+21. Of the 35 case reports in the literature for a karyotype 48,XN,+21,+mar, in only 12 was the origin of the sSMC determined by fluorescence in situ hybridization (FISH)...

OBJECTIVE To determine the pattern of early growth disturbance in chromosomally abnormal fetuses by comparing the volume of the fetal head to that of the trunk. METHODS The fetal trunk and head volume was measured using three-dimensional (3D) ultrasound in 145 chromosomally abnormal fetuses at a median gestational age of 12 (range, 11 + 0 to 13 + 6) weeks. The head volume was measured separat...