13. Summary of ultrasound findings and chromosome abnormalities Flashcards
What can USS diagnose prenatally?
- Chromosome abnormalities
- Neural tube defects (e.g. spina bifida)
- Congenital heart defects
What is the purpose of the first trimester USS?
Check viability of pregnancy, dating, placental localisation, detecting fetal anomalies
What is the significance of nuchal translucency?
Subcutaneous fluid under skin of neck
Most powerful marker of Down syndrome - detects 75-80% of fetuses with abn karyotype
What is increased NT associated with?
T21, T18, T13, Turners - risk increases with increased thickness
What major structural malformations can be detected at first trimester USS?
Holoprosencephaly
Exomphalos
Limb abnormality
Megacystis
What abnormalities are visible for T21 at 18-21 week scan?
Down syndrome
Limb abnormality, brachycephaly, nasal hypoplasia, cardiac defects, duodenal atresia
What abnormalities are visible for T18 at 18-21 week scan?
Edward syndrome
Strawberry shaped head, holoprosencephaly, absent corpus callosum, facial cleft, limb abnormality, exomphalos, megacystis
What abnormalities are visible for T13 at 18-21 weeks scan?
Patau syndrome
Holoprosencephaly, cleft lip & palate, IUGR, microcephaly, cardiac & renal abnormalities, exomphalos, megacystis
What are the features of Turner syndrome on USS?
Large nuchal cystic hygroma, shortening of long bones, generalised oedema, cardiac defects
What are the features of diandry on USS?
Associated with molar pregnancy, rarely persists beyond 20 weeks
What are the features of digyny on USS?
May persist to 3rd trimester
Thin placenta, fetus has severe asymmetric growth restriction
How are fetal abnormalities seen on ultrasound investigated?
QF-PCR for for aneuploidies of 13, 18, 21
Array for CNVs
NGS
Why is it genomic investigation of fetal abnormalities seen on USS important?
Inform management of the pregnancy, guides prognosis and counselling
Other than T13, T18, T21 and Turners, what disorders have features visible at 18-21 week scan?
Wolf-Hirschhorn - 4p-
Cri-du-chat - 5p-
Pallister-Killian - Mosaic tetrasomy 12p (iso12p)
Williams - 7q-
DiGeorge - 22q11 del
What is the diandric phenotype?
Large, cystic placenta
Symmetrical IUGR
Neural tube defects
Oligohydramnios
Normal adrenal glands
High maternal hGC
Generally abort at ~12 weeks
