This document provides an overview of trisomy 18 and trisomy 13, including their causes, clinical presentations, and diagnostic workups. Trisomy 18, also known as Edwards syndrome, is caused by an extra copy of chromosome 18 and results in multiple malformations often incompatible with life. Trisomy 13, also called Patau syndrome, is associated with chromosome 13 and causes severe facial and organ abnormalities. Both conditions can be prenatally diagnosed through tests such as amniocentesis and ultrasound. There is no cure for either trisomy 18 or 13, and many affected fetuses and infants have short life expectancies.

1. trisomy 18 and
trisomy 13
BE BEE
MD

2. Outlines:
1. overview of trisomy 18
2. Clinical presentation of trisomy 18
3. Diagnostic workups
4. Overview of trisomy 13
5. Clinical presentation of trisomy 13
6. Diagnostic workups

3. Trisomy 18—Edwards Syndrome
 a chromosomal disorder caused by the presence of an extra copy of
chromosome 18 in some or all body cells.
 was first recognized and described in 1960 by a British physician, John H.
Edwards
 the second most common chromosomal aberration after Down syndrome.
 associated with multiple malformations, which are often incompatible with life,
combined with psychomotor and cognitive disability.
The prevalence of trisomy 18 varies between 1 in 3,000 to 1 in 8,000 live births
male to female ratio is 1:3.

4. The risk of developing ES increases with the maternal age
Pregnancies with trisomy 18 that reach the third trimester often develop
fetal-growth restriction, and the mean birthweight is <2500.
When undiagnosed, trisomy 18 has resulted in emergency cesarean for “fetal distress” in
nearly 50 percent of cases
median neonatal survival is 8 days, and the 5-year survival rate is 12 percent

5. Most children born with Edwards'
syndrome
appear weak and fragile,
The head is unusually small with prominent
occiput.
The ears are malformed and low-set,
 the mouth and jaw are small (also known as
micrognathia).
cleft palate and lip
clenched fists with the index finger
overlapping the other fingers
club feet, and
toes may be webbed or fused.

6. heart defects in more than 90 percent, particularly ventricular septal defects.
myelomeningocele
 diaphragmatic hernia
omphalocele
 imperforate anus, and
 renal anomalies such as horseshoe kidney

7. Sonographic images of these abnormalities include:
 “strawberry-shaped” cranium,
choroid plexus cysts,
 micrognathia,
clenched hands with overlapping digits,
 radial aplasia with hyperflexed wrists, and
rockerbottom or clubbed feet

8. How Is it Diagnosed?
by the physical abnormalities characteristic to the syndrome
 x-rays may reveal a short breast bone.
 Definitive diagnosis is achieved through karyotyping•
 Edwards' syndrome can be detected before birth ;
If a pregnant woman is older than 35, has a family history of genetic abnormalities, has
previously conceived a child with a genetic abnormality, or has suffered earlier
miscarriages, she may undego Potential tests including MSAFP analysis or screening,
ultrasonography, amniocentesis, and CVS•

9. Is it Treated?
 There is no cure for Edwards syndrome.
90 to 95 % of all babies born with it die within a year of birth.
The few infants that do survive need special treatment--ranging from muscular therapy to
nervous system and skeletal corrections--for their various handicaps

10. Trisomy 13—Patau Syndrome
oIts association with an autosomal trisomy was first described by Patau and
colleagues in 1960.
oThe incidence approximates 1 case in 5000 recognized pregnancies, which
includes abortuses and stillbirths.
o Most affected fetuses are lost or terminated.
o The live birth prevalence is 1 per 12,000 to 18,000
oAt least 80 percent of pregnancies with Patau syndrome result from trisomy 13.
o

11. othe remainder are caused by a robertsonian translocation involving
chromosome 13.
o The most common translocation involves chromosomes 13 and 14,
der(13;14)(q10;q10
owhich is carried by approximately 1 in 1300 phenotypically normal individuals.
o Among translocation carriers, fewer than 2 percent give birth to a live infant
with Patau syndrome.

12. Trisomy 13 may be associated with abnormalities of any
organ system.
Abnormalities of the brain, heart, kidneys, and extremities
are the most frequent.
It may cause severe facial abnormalities. These may include;
o holoprosencephaly (failure of formation of paired cerebral
hemisphere)
o hypotelorism or cyclopia,
o microphthalmia
ocleft lip-palate
o nasal abnormalities that range from a single nostril to a
proboscis.

13.  Cardiac defects are found in up to 90 percent.
 Other abnormalities that suggest trisomy 13
include
omphalocele
 cystic renal dysplasia
 polydactyly,
 rockerbottom feet


14. How it is diagnosed
During the first-trimester screening of trisomy 13, FNT will appear equal or greater than 3.5mm,
with a decreased B-hCG, and PAPP-A. making it undifferentiated from trisomy 18 screening.
Non-invasive prenatal testing (NIPT ) is possible using cell-free DNA in maternal plasma to
differentiate trisomy 18 and 21 from 13
Chorionic villus sampling (CVS) can be performed in an early window between gestational
weeks 11 and 13, while amniocentesis is generally performed in weeks 15 to 18

15. Most gestations with trisomy 13 are terminated, the continuation of pregnancy increases the risk
of preeclampsia.
Continuing pregnancies have at least a 25-percent risk for hypertensive complications
The risk for preeclampsia with severe features is increased more than tenfold and often
develops prior to 32 weeks’ gestation.
Chromosome 13 contains the gene for soluble fms-like tyrosine kinase-1 (sFlt-1), which is an
antiangiogenic protein associated with preeclampsia

16. References;
1.William obstetrics 26th edition
2.basic medical biochemistry a clinical approach 2nd edition
3.Uptudate 2022

17. Thank you