(See also Overview of Chromosomal Anomalies Overview of Chromosomal Anomalies Chromosomal anomalies cause various disorders. Anomalies that affect autosomes (the 22 paired chromosomes that are alike in males and females) are more common than those that affect sex chromosomes... read more .)
Trisomy 13 occurs in about 1/10,000 live births; about 80% of cases are complete trisomy 13. Advanced maternal age increases the likelihood, and the extra chromosome is usually maternally derived.
Infants tend to be small for gestational age Small-for-Gestational-Age (SGA) Infant Infants whose weight is < the 10th percentile for gestational age are classified as small for gestational age. Complications include perinatal asphyxia, meconium aspiration, polycythemia... read more . Midline anomalies are common and include holoprosencephaly Holoprosencephaly Cerebral hemispheres may be large, small, or asymmetric; the gyri may be absent, unusually large, or multiple and small. In addition to the grossly visible malformations, microscopic sections... read more 
(failure of the forebrain to divide properly), facial anomalies such as cleft lip and cleft palate Cleft Lip and Cleft Palate An oral-facial cleft is a birth defect in which the lip, the roof of the mouth, or both do not close in the midline and remain open, creating a cleft lip and/or cleft palate. These defects are... read more 
, microphthalmia Microphthalmia Eyes can be absent, deformed, or incompletely developed at birth, often in conjunction with other congenital abnormalities and syndromes. (See also Introduction to Congenital Craniofacial and... read more 
, colobomas Coloboma Eyes can be absent, deformed, or incompletely developed at birth, often in conjunction with other congenital abnormalities and syndromes. (See also Introduction to Congenital Craniofacial and... read more (fissures) of the iris, and retinal dysplasia. Supraorbital ridges are shallow, and palpebral fissures usually are slanted. The ears are abnormally shaped and usually low-set. Hearing loss is common. Scalp defects and dermal sinuses are also common. Loose folds of skin often are present over the back of the neck.
A single transverse palmar crease, polydactyly Polydactyly Congenital limb defects involve missing, incomplete, supernumerary, or abnormally developed limbs present at birth. (See also Introduction to Congenital Craniofacial and Musculoskeletal Disorders... read more 
, and hyperconvex narrow fingernails are also common. About 80% of cases have severe congenital cardiovascular anomalies Overview of Congenital Cardiovascular Anomalies Congenital heart disease is the most common congenital anomaly, occurring in almost 1% of live births ( 1). Among birth defects, congenital heart disease is the leading cause of infant mortality... read more 
; dextrocardia is common. Genitals are frequently abnormal in both sexes; cryptorchidism Cryptorchidism Cryptorchidism is failure of one or both testes to descend into the scrotum; in younger children, it is typically accompanied by inguinal hernia. Diagnosis is by testicular examination, sometimes... read more 
and an abnormal scrotum occur in boys, and a bicornuate uterus occurs in girls.
Apneic spells in early infancy are frequent. Intellectual disability Intellectual Disability Intellectual disability is characterized by significantly subaverage intellectual functioning (often expressed as an intelligence quotient < 70 to 75) combined with limitations of adaptive... read more is severe.
Diagnosis of Trisomy 13
Cytogenetic testing by karyotyping, fluorescent in situ hybridization (FISH) analysis, and/or chromosomal microarray analysis
(See also Next-generation sequencing technologies Genetic Diagnostic Technologies Genetic diagnostic technology is rapidly improving. A small amount of DNA can be amplified using the polymerase chain reaction (PCR) process, which can produce millions of copies of a gene or... read more .)
Diagnosis of trisomy 13 may be suspected postnatally by appearance or prenatally by abnormalities on ultrasonography Prenatal Ultrasonography All procedures used to diagnose genetic disorders, except ultrasonography, are invasive and involve slight fetal risk. If testing detects a serious abnormality, the pregnancy can be terminated... read more (eg, intrauterine growth restriction), or by increased risk noted on multiple marker screening or noninvasive prenatal screening Screening Chromosomal anomalies cause various disorders. Anomalies that affect autosomes (the 22 paired chromosomes that are alike in males and females) are more common than those that affect sex chromosomes... read more (NIPS) using cell-free fetal DNA analysis on a maternal blood sample.
Confirmation is by cytogenetic testing (karyotyping, FISH analysis, and/or chromosomal microarray analysis) of samples obtained by chorionic villus sampling Chorionic Villus Sampling All procedures used to diagnose genetic disorders, except ultrasonography, are invasive and involve slight fetal risk. If testing detects a serious abnormality, the pregnancy can be terminated... read more or amniocentesis Amniocentesis All procedures used to diagnose genetic disorders, except ultrasonography, are invasive and involve slight fetal risk. If testing detects a serious abnormality, the pregnancy can be terminated... read more . Postnatally, confirmation is by cytogenetic testing usually of a blood sample.
Confirmatory testing is offered in cases suspected based on NIPS. Management decisions, including termination of pregnancy, should not be made based on NIPS testing alone. See also The American College of Obstetricians and Gynecologists Committee on Practice Bulletins–Obstetrics, Committee of Genetics, and the Society for Maternal–Fetal Medicine 2020 practice bulletin regarding cell-free fetal DNA testing.
Treatment of Trisomy 13
Supportive care
Most patients (80%) are so severely affected that they die before age 1 month; < 10% survive longer than 1 year. Support for the family is critical.
More Information
The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.
American College of Obstetricians and Gynecologists Committee on Practice Bulletins–Obstetrics, Committee of Genetics, and the Society for Maternal–Fetal Medicine: Screening for fetal chromosomal abnormalities: ACOG practice bulletin, number 226 (2020)
SOFT (Support Organization for Trisomy 18, 13, and Related Disorders): An organization providing resources, research information, and community and support services to people caring for others who have trisomy 18, 13, or another related chromosome disorder
