Chapter 24 Obstetric and perinatal infections

Question 1

Why does the fetus have poor immune defenses?

Answer 1

• IgM and IgA antibodies are not produced in significant amounts until the second half of pregnancy
• there is no IgG antibody synthesis
• cell-mediated immune responses are poorly developed or absent, with inadequate production of the necessary cytokines

Question 2

What is tested for in routine antenatal screening?

Answer 2

rubella Ab, treponemal Ab (includes syphilis, yaws, pinta or bejel, which cannot be identified individually by serology), hepatitis B surface antigen and HIV combination Ab and Ag assays

Question 3

What treatment is offered for an HIV-positive diagnosis in an expecting mother?

Answer 3

Discuss antiretroviral therapy for the mother and, immediately on brith, the child, planning a vaginal birth unless C-section is indicated, advising against breastfeeding to reduce risk of vertical transmission, child will be followed up for at least 12 months for HIV

Question 4

What is the treatment for a chronic hepatitis B virus-positive mother?

Answer 4

Upon determining the maternal level of infectivity, the baby is offered an accelerated course of hepatitis B vaccine or vaccine and HBV-specific Ig if the mother is highly infectious. Antiviral drugs for chronic hepatitis B might be offered, together with long-term follow-up, to the mother.

Question 5

What is the treatment for a treponemal-positive mother?

Answer 5

antibiotics, baby is followed up for the first year

Question 6

How does risk of congenital rubella infection and risk of adverse fetal outcome change throughout the pregnancy?

Answer 6

90% at under 11 weeks, 55% at 11-16 weeks, 45% at more than 16 weeks and no risk after 20 weeks.
Adverse outcome risk: 90% under 11 weeks, 20% at 11-16 weeks, low at >16 weeks, no increased risk after 20 weeks.

Question 7

What are the general defects on an embryo with congenital rubella?

Answer 7

low birth weight, failure to thrive, increased infant mortality

Question 8

What malformations are seen in embryos with congenital rubella?

Answer 8

small brain size, mental retardation, cataract, microphthalmia, hearing defect, organ of Corti affected, patent ductus arteriosus, patent interventricular septum

Question 9

What lesions are seen in embryos with congenital rubella?

Answer 9

hepatosplenomegaly, thrombocytopenic purpura, anemia

Question 10

Why is pregnancy a contraindication for the MMR vaccine?

Answer 10

It is a live vaccine

Question 11

Which vaccine is given to protect an as yet non-existent individual (fetus) since infection is subclinical or mild in the mother?

Answer 11

rubella (MMR)

Question 12

Which neonatal infection is second only to Down’s syndrome as a cause of intellectual disability?

Answer 12

CMV

Question 13

How is congenital CMV diagnosed?

Answer 13

Detecting CMV-specific IgM antibodies in infant blood within 3 weeks of delivery, and by detecting and quantifying CMV DNA in blood or urine during this period. Virus can also be isolated from throat swab or urine sample

Question 14

How is congenital CMV treated?

Answer 14

ganciclovir and valganciclovir can be considered in managing symptomatic babies with congenital CMV

Question 15

What is the vector for Zika virus?

Answer 15

Aedes aegypti mosquito

Question 16

How can Zika viruses be spread vertically and horizontally?

Answer 16

can cross placenta and maternal infection contracted during pregnancy can result in fetal malformations and congenital malformations and congenital microcephaly. Sexual transmission of Zika virus has occurred.

Question 17

What are the clinical features of syphilis in the infant?

Answer 17

rhinitis, skin and mucosal lesions, hepatosplenomegaly, lymphadenopathy, abnormalities of bones, teeth and cartilage (saddle-shaped nose)

Question 18

How can vertical transmission of Zika virus be prevented?

Answer 18

Since vertical transmission most commonly takes place after 4 months of gestation, treatment of the mother before the fourth month of pregnancy should prevent fetal infection

Question 19

What determines the severity of congenital toxoplasmosis?

Answer 19

fetal damage more severe the earlier in the pregnancy the infection is contracted

Question 20

What are the clinical features of congenital toxoplasmosis in severely affected infants?

Answer 20

convulsions, microcephaly, chorioretinitis, hepatosplenomegaly, jaundice, with later hydrocephaly, MR and defective vision

Question 21

How can congenital toxoplasmosis be avoided?

Answer 21

avoidance of primary infection which occurs by ingesting cysts from cat feces

Question 22

What proportion of infants born to HIV-infected mothers in resource-poor countries are infected, and in what stage of pregnancy do the infections take place?

Answer 22

~1/4; late pregnancy or during delivery

Question 23

How does congenital HIV infection manifest in the newborn?

Answer 23

poor weight gain, susceptibility to sepsis, developmental delays, lymphocytic pneumonitis, oral thrush, enlarged lymph nodes, hepatosplenomegaly, diarrhoea and pneumonia, and some infants develop encephalopathy and AIDS by 1 year of age.

Question 24

What effects would infection of the placenta with Listeria have?

Answer 24

abortion, premature delivery, neonatal septicemia or pneumonia with abscesses or granulomas

Question 25

Which neonatal infections were noted in this chapter?

Answer 25

Neisseria gonorrhoeae, Chlamydia trachomatis, HSV, genital papillomavirus, Group B Streptococci, Gram-negative bacilli, Candida albicans

Question 26

Around 1847 Ignaz Semmelweiss introduced aseptic technique (handwashing) during labor and delivery at a time when what was the major cause of maternal death in Europe?

Answer 26

puerperal sepsis (6 weeks after childbirth)

Question 27

What caused puerperal fever, a cause of 10% of maternal death in 19th century Europe?

Answer 27

• group A beta-haemolytic streptococci were the major culprits and came from the nose, throat or skin of hospital attendants
• other possible organisms include anaerobes such as Clostridium perfringens or Bacteroides, E. coli and group B streptococci and originate from the mother’s own faecal flora

Question 28

What neonatal infections can be transmitted to the newborn during the first 1-2 weeks after birth, rather than during delivery

Answer 28

• Group B beta-haemolytic streptococci and Gram-negative bacilli (see above) acquired by cross-infection in the nursery can still cause serious infection at this time, often with meningitis
  
  • Herpes simplex virus from facial cold sores or herpetic whitlows of attending adults
  • Staphylococci from the noses and fingers of adult carriers may cause staphylococcal conjunctivitis or ‘sticky eye’, skin sepsis in the neonate, and sometimes the staphylococcal ‘scalded skin’ syndrome due to a specific ‘epidermolytic’ staphylococcal toxin

Question 29

What causes neonatal tetanus?

Answer 29

If hygienic practices are poor, the umbilical stump, especially in resource-poor countries, may be infected with Clostridium tetani, usually because instruments used to cut the cord are contaminated with bacterial spores

Question 30

What causes breast abscess during the first 1-2 weeks of life?

Answer 30

Staph aureus that colonizes nose of infant enters nipple during feeding