Trisomies

Incidence for trisomy 13:

-1/5000-1/20,000 live births -Accounts for up to 1% of first trimester miscarriages

Incidence of trisomy 18:

-1/8000 births -2nd most common autosomal trisomy -95% of cases result in stillbirth or spontaneous abortion

Most common defects with trisomy 13:

-CNS anomalies -Cardiac anomalies -Facial anomalies -IUGR -Holoprosencephaly -Extremity abnormalities -Renal abnormalities

Clinical features with trisomy 18:

-Cardiac defects -IUGR -Prominent occiput -Small mouth -Micrognanthia -Low and pointed ears -Mental retardation -Clenched hands, overlapping fingers -Short sternum -Rocker-bottom feet

What is the prognosis for trisomy 13?

-Extremely poor -82% of infants die in first month -5% may survive the first 6 months

Prognosis for trisomy 18:

-Extremely poor -Recurence rate less than 1%

Testing availability for trisomy 21

-First trimester nuchal translucency is least invasive and gaining popularity -Second trimester amniocentesis -First trimester CVS

Prognosis and survival rate for trisomy 21:

-Good prognosis -Average of 55 year survival rate -Recurrance rate approx 1%

Differential diagnosis with trisomy 13:

-Meckel Gruber Syndrome has similar presentation and has 25% recurrence rate

Clinical features with trisomy 13:

-Microcephaly -CNS anomalies (abnormal posterior fossa, ventriculomegaly, agenesis of corpus callous, holoprosencephaly) -Cardiac defects > 80% -IUGR -Ocular abnormalities (especially midline) -Cleft lip and palate 60-70% -Limb deficiencies -Rocker-bottom or club feet -Clenched hands, polydactyly -Omphalocele Renal anomalies

Incidence of trisomy 21:

-Overall 1/800 -1/504 in US -1/274 in women over 35 years old -1/10 in women 48 years or older -Most common autosomal trisomy in live born infants

Most common ultrasound features with trisomy 18:

-Short ear length -Clenched hands -CNS 87% -IUGR 50%

Clinical features for trisomy 21:

-Short stature -Redundant nuchal skin -Flat, small nose -Simian crease (single palmar crease) -Brachycephaly -Flat occiput -Protruding tongue -Cardiac defects -Hydrocephalus -Gastrointestinal abnormalities

Most common ultrasound findings with trisomy 21:

-Thickened nuchal fold 50% -Cardiac abnormalities (ASD, VSD, endocardial cushion defects) -Short femurs -Echogenic bowel -Duodenal atresia -Hypoplastic middle phalanx of the 5th digit -2 vessel cord -Absent nasal bone

Trisomy 21 is also known as:

Down's Syndrome

Trisomy 18 is also known as:

Edwards Syndrome

Trisomy 13 is also known as:

Patau Syndrome