60. Pathology of pregnancy II (transplacental infections, chromosomal aberrations)

Page created on May 3, 2019. Last updated on May 5, 2019 at 20:35

Placental infections

Infections may reach the placenta by ascension through the birth canal or by transplacental spread. The placenta is comprised of many parts and we must therefore introduce a few new terms:

• Chorioamnionitis – infection of the foetal membranes
• Funisitis – infection of the umbilical cord
• Villitis – infection of the placental villi

Ascending infections of the placenta are much more common than transplacental ones. These infections are often caused by Mycoplasma, Candida and bacteria of the normal vaginal tract. These pathogens ascend through the birth canal, cause the foetal membranes to rupture and then infect the membranes, causing chorioamnionitis. The foetus then “inhales” the infected amniotic fluid. If the infection progresses beyond the membranes it can cause funisitis and villitis. Ascending placental infection can cause complications like sepsis in both the mother and the foetus and pneumonia in the foetus.

Transplacental infections of the placenta are caused by the TORCH complex. This involves the following pathogens:

• Toxoplasmosis
• Others
  • Syphilis
  • Varicella
  • Parvovirus B19
• Rubella
• Cytomegalovirus
• Herpes simplex virus

Any of these pathogens can be transmitted from mother to foetus during pregnancy through the placenta. These infections often cause villitis. TORCH infections have many complications:

• Spontaneous abortion
• Premature birth
• Mental retardation
• Cataracts
• Congenital heart disease

Down syndrome

Down syndrome is caused by trisomy 21. All cells in a person with Down syndrome have 47 chromosomes instead of the normal 46. This chromosomal aberration occurs spontaneously during meiosis and is not hereditary.

Epidemiology: It occurs in 1 in 700 live births. The risk for trisomy 21 increases drastically with the age of the mother. The incidence is 1:1500 in mothers aged 20 but 1:100 in mothers aged 40 and 1:6 in mothers aged 50.

Prognosis: People with trisomy 21 have a decreased life expectancy, around 50 years. This is mostly due to organ malformations and immunodeficiency, which are common.

Clinical features:

• Craniofacial dysmorphia
  • Increased distance between eyes
  • Broad and flat nasal bridge
  • Cataracts
  • Astigmatism
• Organ malformations
  • Congenital heart defects – occurs in 50% of cases
    • Atrioventricular septal defect
    • Ventricular septal defect
    • Atrial septal defect
  • Hirschsprung disease
  • Duodenal stenosis
  • Hypogonadism
  • Hypothyroidism
• Development
  • Decreased IQ
  • Delayed motor development
  • Short stature
  • Obesity
• Increased risk for disease
  • Increased risk of acute lymphoblastic/myeloid leukaemia
  • Increased risk of Alzheimer disease
  • Increased risk for infections

Edwards syndrome

Edwards syndrome is caused by trisomy 18. It occurs every 60 00 live births. Like for Down syndrome the risk of getting this syndrome increases with maternal age. Affected persons have:

• Prominent occiput
• Low ears
• Mental retardation
• Congenital heart defects
• Renal malformations

Few affected infants survive past 12 months of age.

Patau syndrome

Patau syndrome is caused by trisomy 13. It occurs every 10 000 live births. Like for Down syndrome the risk of getting this syndrome increases with maternal age. Affected persons have:

• Microcephaly
• Mental retardation
• Congenital heart defects
• Renal malformations

Few affected infants survive past 6 months of age.

DiGeorge syndrome

DiGeorge syndrome is caused by deletion of a small segment of chromosome 22, more specifically 22q11.2. Affected persons have:

• Congenital heart defects
• Delayed development
• Impaired T cell immunity due to thymic hypoplasia
• Hypocalcaemia due to parathyroid hypoplasia

Affected individuals have normal life expectancy if treated.

Cri du chat syndrome

Cri du chat syndrome is caused by deletion of a small segment on the short arm of chromosome 5. The name of the conditions means “the cat’s cry” in French. The name comes from the cat-sounding cry affected infants have. Affected persons also have:

• Congenital heart defects
• Mental retardation

Affected individuals can have normal life expectancy if treated.

Klinefelter syndrome

Klinefelter syndrome is caused by the presence of one (or more) extra X chromosomes in men, resulting in a 47XXY (rarely 48XXXY) karyotype. These males have testicular hypoplasia and hypogonadism, which reduces their testosterone levels. Affected people have:

• Gynecomastia
• Reduced fertility
• Increased risk for diseases that usually affect females
  • Autoimmune disorders
  • Breast cancer
  • Osteoporosis

Treatment involves testosterone replacement therapy. The life expectancy is normal.