Dating Scan for increased risk from Maternal Serum Screening

Ultrasound scanning guidelines

Dating Scan for increased risk from maternal serum screening (MSS) A scan may be requested after maternal serum screening (MSS) indicates an increased risk for chromosomal abnormalitiy (down syndrome, neural tube defect, abdominal wall defect) Often performed about 16 weeks gestation (this is when MSS is performed) The primary purpose of this scan is to provide accurate dates for the pregnancy In addition to fetal biometry, a limited assessment of anatomy should be performed if there is an increased risk of NTD/abdominal wall defect Assess: Fetal number Fetal cardiac activity Placental position Liquor volume Adnexae Cervix Fetal biometry Documentation: Placental views long / trans Internal os view in the midline with a measurement to lower placental edge Deepest pool of liquor with AP measurement Full length of fetal head and body BPD, HC, AC, FL Fetal heart in thorax / clipstore of fetal heart activity +/- M-mode Additional Documentation - for increased risk of NTD/abdominal wall defect on MSS Fetal cord insertion Coronal or sagittal views of the entire spine Trans assessment of entire spine Cerebellum / Cisterna Magna Choroid plexus / lateral ventricle measurement at trigone

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