Diagnostic ultrasound ( PDFDrive )

CHAPTER 31 Chromosomal Abnormalities 1109
membrane rupture, and talipes equinovarus as well as higher
amniotic luid culture failures and therefore is not recommended.
254 As with all fetal procedures, the fetal heart rate is
documented ater the procedure. Women who are Rh negative
and have an Rh-positive partner are given RhoGAM.
CONCLUSION
Over the past three decades, risk assessment for aneuploidy has
progressed to the point that maternal age alone or NT width
alone is no longer considered adequate for determining the risk
of having a chromosomally abnormal ofspring. Obstetric
sonography, in conjunction with maternal serum analytes, has
become a powerful tool in the assessment aneuploidy risk in
both the irst and the second trimester. In the second trimester
the diverse sonographic patterns seen with the diferent aneuploidies
allow clinicians to guide patients to a presumptive
diagnosis. Recent advances in cell-free DNA analysis provide
exceptional screening performance targeted speciically for
trisomies 21 and 18 and, to a slightly lesser degree, for trisomy
13; however, other chromosomal abnormalities that are potentially
detected by combined screening or diagnostic testing are not
identiied. Karyotype has been the standard for fetuses with
structural anomalies; however, microarray analysis to determine
CNV abnormalities will augment the detection of clinically
signiicant disorders, most notably in fetuses with structural
abnormalities. When considering all detectable chromosome
problems, multiple marker screening including NT, with the
option of diagnostic testing for screen positive results, is the
optimal strategy for most women. For pregnant women aged 40
years or older, cell-free DNA as a primary screening tool is
optimal. 4
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