Lecture 51: Obstetric and Perinatal Infections Flashcards
what acts as an immunological barrier in pregnancy
placenta
how does placenta act as an immunological barrier
allows the mixing of fetal and maternal blood w/o outright immune/inflammatory response to fetus from mother
how does placenta act as an immunological barrier
- reduced expression of class 1 MHC antigens on placental cells
- syncytium blocks transit of immune cells
- inhibition of T cells
- allows the mixing of fetal and maternal blood w/o outright immune/inflammatory response to fetus from mother
what is the placental syncytium
outer layer of the placenta in contact w/ maternal blood
describe the adjustment in maternal immune system during pregnancy
- down regulation in TH1 and natural killer (NK) cells
what are TH1 cells
CD4 effector T cells involved w/ response to intracellular pathogens e.g. viruses and some bacteria
what are NK cells
- natural killer cells
- innate immune response to virally infected cells acting by secreting interferons and tumour necrosis factor alpha
outline some of the consequences of adjustment in maternal immune system during pregnancy
- consequence for disease
- increased likelihood of severe symptomatic poliovirus or severe Hep A
- rheumatoid arthritis often ameliorates
- systemic lupus erythematosus can flare up
what would happen ig maternal immune system were fully functional
allograft rejection i.e. rejection of fetus
describe the fatal immune system in utero
- fetal IgM and IgA Ab not prod in significant amounts until second 1/2 of pregnancy
- fetal IgG Ab synthesis lacking
- Fetal CMI absent
- baby not considered to have significant cell mediated immunity
- baby can me exposed to maternal IgG which can add a certain amount of protection to baby
what would happen if fetal immune system were fully functional
allograft vs host rejection
list some infections that are moire severe in pregnancy and why are they more severe
- malaria
- flu
- UTI (esp asc. UTI)
- candidiasis
- listeriosis
- varicella
they affect both mother and fetus
outline how malaria can be so severe in pregnancy
- plasmodium infected erythrocytes accumulate in placenta
- non immune/partially immune women can have severe infections
- functioning of placenta is impaired
give categories of mother to baby transmission
- intrauterine (transplacental) infection
- -> during pregnancy
- perinatal transmission
- -> during birth
- post natal transmission e.g. HTLV (human T-lymphotropic virus) from breastmilk
give some examples of congenital infections that can occur via intrauterine transmission
- rubella
- parvovirus B19
- CMV
- syphilis (treponema palidum)
- toxoplasma gondii
- varicella zoster virus
think TORCH
T - toxoplasma gondii O - others e.g. parvovirus B19, syphillis varicella zoster R - rubella C - CMV H - herpes
give some examples of congenital infections that can occur via perinatal transmission
- HIV
- HBV
- group B strep
- listeria monocytogens
- chlamydia trachomatis
- neisseria gonorrhoeae
(some bacteria can colonise in vaginal fluid and then infect baby during passage through birth canal)
describe rubella infection
- incubation period 14-21 days
- mild disease; fever, malaise
- irr. maculopapular rash (lasts 3 days)
- lymph nodes behind ear
- arthralgia
- infection is commonly subclinical (in adults and children)
describe how rubella is vaccinated against
- live attenuated vaccine
- part of MMR vaccine
describe congenital rubella syndrome
- maternal infection <16 weeks gestation (1st trimester)
- ~80% suffer from sensorineural deafness
- ~25% develop insulin-dependent diabetes mellitus later in life
- can develop cataracts, brain and heart problems
- infant sheds virus into throat and urine for many months and is very infectious
how is rubella virus detected in infants
PCR from various specimen sites incl. nasopharynx
describe erythrovirus/parvovirus B19 infection
- febrile illness in children and maculopapular rash on face
- -> ‘slapped cheek syndrome’
- -> aka ‘erythema infectiosum’ or ‘5th disease’
- symptomless infection common in pregnancy
describe B19 infection in pregnancy
- danger is maternal infection weeks 10-20
- fetal anaemia
- HF –> hydrops foetalis
- -> swollen macerated pale fetus - fatal outcome
- -> cause of “non-immune hydrops” among other things
- risk about 10% if infection @10-20 weeks
outline the concern, investigations done, and action taken if a pregnant women comes in contact w/ a rash
- focus is on B19 and rubella
- blood sample taken from mother
- check IgG and IgM to both viruses
- -> looking for immunity AND current infection
- -> if non immune repeat 4 weeks after contact
- B19 can be treated w/ intrauterine blood transfusion
- rubella; termination options –> further tests can help define risk
describe congenital CMV
- 1/100 babies born congenitally infected w/ CMV
- urine CMV PCR +ve at birth
- majority fine
- can have congenital CMV syndrome which has a wide spectrum of severity
what is the key test for congenital CMV
urine PCR
describe maternal CMV infection
primary acquired infection:
- higher risk of severe neonatal disease
reactivation infection:
- lower risk of neonatal disease
what virus family is CMV part of
herpes family
describe the spectrum of severity for CMV
severe:
- CMV inclusion disease
- -> can affect liver, spleen, blood, brain, eyes
mild:
- asymptomatic
- unilateral sensineural deafness
describe the diagnosis of congenital CMV
maternal diagnosis:
- serology
- seroconversion
- using booking blood (blood taken when women books into maternity services at start of pregnancy) as baseline to check for immunity
baby diagnosis:
- PCR urine first week of life
describe inclusion disease w/ CMV
widespread calcification of tissues
describe the affect of syphilis infection during pregnancy
maternal infection:
- miscarriages, premature births, stillbirths, death of newborn
- congenital syndrome
- -> affects teeth, brain, ears, bones
- -> hepatosplenomegaly, jaundice, anaemia
what is the treatment for maternal syphilis infection during pregnancy
high doses of penicillin
what is toxoplasma gondii and how can it infect people
- protozoan parasite
- from undercooked meat and cat faeces
describe maternal infection of toxoplasma gondii in pregnancy and its effect
- risky to fetus in all 3 trimesters
- multiple problems in baby
- -> spectrum; asymptomatic to severe
- -> treated w/ drugs
what does varicella zoster virus cause
chickenpox
describe the effect of varicella infection during pregnancy to mother and baby
- congenital varicella syndrome (<20 weeks gestation) limb deformities, serious brain fan eye abnormalities
- can also cause serious infection in pregnant women
- -> maternal pneumonitis
what is done if a pregnant woman is exposed to chickenpox
- test for immunity (VZV IgG)
- -> 90%+ are immune
- -> lots of people have no memory of chickenpox
- if non immune (VZV IgG -ve)
- -> offer VZIG (varicella zoster immunoglobulin)
- -> human antibody product
- -> IM injection
outline UK antenatal screening
in NI test for:
- HBV –> HBsAg (assess current infection)
- HIV –> HIV Ag/Ab (assess current infection)
- syphilis –> T palidum total Ab (specific test) (assess infection past or present)
- Rubella –> IgG (assess immunity)
- single blood sample, booking blood, 13 weeks gestation
what is initially done if pregnant woman is HBsAg +ve and why
- do specific markers and HBV DNA
- -> E antigen +ve more likely to transmit (95% transmit if no intervention)
- -> high DNA more likely to transmit
what is the intervention if pregnant woman is HBsAg +ve
- HBV vaccine for baby
- +/- specific immunoglobulin
- -> ~100% effective in preventing MTB transmission
- -> need to follow up baby at 1yo
what is initially done if pregnant woman is HIV +ve
do HIV viral load
what is the intervention if pregnant woman is HIV +ve
- antiretroviral drugs for mother and baby
- elective Caesarean section (unless VL undetectable)
- no breast feeding
- all to minimise blood/body fluid sharing between mother and baby
- no intervention; MTB transmission = 25%
- intervention; MTB transmission = <1%
- need to follow up baby regularly with PCR and antibody –> all clear @ 18 months
what is initially done if pregnant woman is syphilis +ve
confirmatory serology
what is the intervention if pregnant woman is syphilis +ve
- treat mother w/ penicillin
- possibly treat baby too
- follow up baby
- -> antibody - look for falling levels and eventually disappearance
what is done if pregnant woman is rubella non immune
offer MMR vaccination AFTER pregnancy
–> to protect next pregnancy
outline some infections that can occur at the time of birth
- chorioamnionitis; maternal fever, premature delivery and still birth
- -> bacteria involved incl. group B haemolytic strep among others
- bacterial meningitis is frequently fatal unless treated
- neonatal varicella - maternal chickenpox (7days before/after delivery) - rare
- HSV infection (relatively rare in UK)
what is chorioamnionitis
infection of uterine membranes assc. w/ pregnancy
outline perinatal infection w/ STIs
- neonatal conjunctivitis (caused by neisseria gonorrhoeae/chlamydia trachomatis)
- neonatal conjunctivitis = ophthalmia neonatorum
- C trachomatis can lead to pneumonia ~2 weeks of age
give examples of neonatal infections that can cause sepsis and/or meningitis
- group B strep
- listeria monocytogenes
- E coli
- enteroviruses and parechoviruses
describe the cause and effects of congenital and neonatal listeriosis
- listeria monocytogenes is gram +ve rod; motile and beta-haemolytic
- can live at fridge temp
- maternal flu and bacteraemia –> fetal infection, abortion, premature delivery, neonatal septicaemia, pneumonia w/ accesses or granulomas
- early onset neonatal meningitis
- grown from blood cultures, CSF or newborn skin lesions
what is the treatment of congenital and neonatal listeriosis
amoxicillin
- may need to be combined w/ gentamicin to achieve bactericidal effect
describe maternal listeria infection
- many pregnant women can carry listeria asymptomatically in GIT or vagina
how can fetal infection of listeria occur from mother
transplacental transmission
what effect can group B strep have on neonate
septicaemia or meningitis
describe group B strep presence in women
part of normal flora of gut and genital tract and is found in 20-40% women
give an example of post natal maternal infection
puerperal sepsis
what is puerperal sepsis
sepsis of uterus and genital tract post partum
puerperal = period of 6 weeks after childbirth; mother’s reproductive organs return to original condition
what organisms can cause puerperal sepsis
- strep pyogenes (group A strep)
- clostridium perfringens
- Ecoli
- group B strep
who do mothers need to be careful being in contact with after birth to avoid getting group A strep infection
people w/ sore throats
how can puerperal sepsis be diagnosed
Infection of the genital tract occurring at any time between the rupture of membranes or labour, and the 42nd day postpartum in which 2 or more of the following are present:
- pelvic pain
- fever = >38.5C
- abnormal vaginal discharge e.g. pus
- abnormal smell of discharge
- delay in the rate of reduction of uterus size (<2cm/day during first 8 days)
what is the general approach to microbiology investigation
- if inflamed organ site identified, take samples from that site
- if suspect severe infection/sepsis, take a blood culture (regardless of px temperature)
how to check for viral infection in baby
- 4mls clotted blood (serological) or EDTA blood (PCR or nucleic acid amplification)
- urine (CMV PCR)
