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A reassessment of biochemical marker distributions in trisomy 21-affected and unaffected twin pregnancies in the first trimester.
MedLine Citation:
PMID:  20878678     Owner:  NLM     Status:  In-Process    
OBJECTIVE: To estimate the difference between levels of the two biochemical markers pregnancy-associated plasma protein-A (PAPP-A) and maternal serum free β-human chorionic gonadotropin (free β-hCG) in twin pregnancies relative to singleton pregnancies and establish an improved screening procedure for chromosomal abnormalities such as trisomy 21 in twin pregnancies.
METHODS: 4843 unaffected and 47 trisomy 21-affected twin pregnancies were included in the study. Chorionicity-specific medians were generated for PAPP-A and free β-hCG from gestational ages 8 to 14 weeks. Multiple of the median values for each of the biochemical markers were calculated. Detection rates and false-positive rates were estimated for screening tests incorporating nuchal translucency and maternal age, with and without biochemistry.
RESULTS: Medians for the two biochemical markers for monochorionic and dichorionic twins in unaffected pregnancies show a gestational age-specific increase relative to singleton medians. Allowing for gestation and chorionicity, twin pregnancies affected with trisomy 21 had higher levels of free β-hCG and lower levels of PAPP-A. Adding biochemistry into the risk assessment using a fixed risk cut-off of 1 in 100 increased the detection rate for fetal trisomy 21 in dizygotic twin pregnancies from 78 to 90%, and decreased the false-positive rate from 8.0 to 5.9%.
CONCLUSION: Generation of chorionicity-specific medians for the biochemical markers and their use in risk assessment can improve the performance of first-trimester screening for chromosomal abnormalities in twins to a level comparable with that in singleton pregnancies.
H N Madsen; S Ball; D Wright; N Tørring; O B Petersen; K H Nicolaides; K Spencer
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Ultrasound in obstetrics & gynecology : the official journal of the International Society of Ultrasound in Obstetrics and Gynecology     Volume:  37     ISSN:  1469-0705     ISO Abbreviation:  Ultrasound Obstet Gynecol     Publication Date:  2011 Jan 
Date Detail:
Created Date:  2010-12-24     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9108340     Medline TA:  Ultrasound Obstet Gynecol     Country:  England    
Other Details:
Languages:  eng     Pagination:  38-47     Citation Subset:  IM    
Department of Clinical Biochemistry, Aarhus University Hospital, Skejby, Denmark.
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