Impact of the virus on the fetus and gestational age
The teratogenic effect of the pathogen is most pronounced in early pregnancy. The earlier the infection occurs, the higher the probability of severe anomalies or fetal demise. The risk of congenital malformations is distributed as follows:
- 1st week of gestation: fetal damage is observed in 75–80% of cases.
- 2–4 weeks: the risk is approximately 61%.
- 9–13 weeks (early gestation): the probability decreases to 8–30%.
- Fourth month: the frequency of malformations drops to 1.4–5.7%.
- Fifth month and later: risks are minimal (0.4–1.7%).
Intrauterine infection is also associated with a high rate of stillbirths. In the first trimester, this figure is about 10%, in the second — 5%, and in the third — about 2%.
Clinical picture and long-term consequences
The prognosis for a newborn with confirmed CRS is always serious. The disease is characterized by the formation of the classic triad, which includes:
- Cataracts (severe visual impairment).
- Deafness.
- Congenital heart defects.
A distinct problem is progressive rubella panencephalitis (PRPE) — a fatal neurological disease historically described specifically as a late complication of CRS. The infection follows a slow-virus pattern: the virus persists in neurons for a long time, and the disease itself manifests only in the second decade of life.
The patient gradually loses cognitive functions (dementia develops), motor disorders appear (facial nerve paresis, increased muscle tone, loss of the ability to stand). At the same time, sensory impairments are completely absent. The outcome of PRPE is 100% fatal.
Pathogenesis of CNS lesions
The development of rubella panencephalitis is based on the direct cytopathic effect of the virus on neurons, axons, and oligodendrocytes, as well as an aggressive immune response.
The synthesis of specific antibodies occurs directly in the brain tissue with an intact blood-brain barrier (BBB). Lymphocytic infiltrates form around blood vessels, and exudative-productive vasculitis develops. This leads to massive demyelination and degenerative-atrophic changes. Pleocytosis, elevated total protein, and high titers of specific IgGs are recorded in the cerebrospinal fluid (CSF) of such patients.
Diagnostic challenges in pregnant women
Clinically suspecting the infection in the mother can be extremely difficult. An atypical course — complete absence of rash — is observed in 20–30% of patients. In addition, there are inapparent (asymptomatic) forms of infection. Even with a manifest course in adults, the exanthema often merges into erythematous fields, which requires differential diagnosis with measles and scarlet fever.
For this reason, laboratory verification methods play a decisive role:
- PCR diagnostics: the main method for early confirmation. Viral genetic material can be isolated from saliva, urine, nasopharyngeal swabs, or blood plasma.
- ELISA (determination of IgM and IgG): specific IgMs appear from the 3rd–4th day of the disease and disappear after 4–5 weeks.
- IgG avidity index: a crucial indicator for pregnant women. Low-avidity antibodies (index less than 30) indicate a recent encounter with the virus (acute infection). High-avidity antibodies (index greater than 60) indicate that the infection was contracted more than 6 weeks ago, and there is currently no risk to the fetus.
Briefly: answers to topical questions
Which specific congenital heart defects are most typical for congenital rubella syndrome?
Common congenital heart defects in congenital rubella syndrome include:
- Patent ductus arteriosus (botryoid duct).
- Pulmonary trunk stenosis / pulmonary artery stenosis.
- Ventricular septal defect.
- Atrial septal defect.
What delayed (late) manifestations and complications, besides panencephalitis, are characteristic of patients with congenital rubella?
Long-term endocrine complications of congenital rubella syndrome include the development of diabetes mellitus.
- Insulin-dependent diabetes mellitus — prior congenital infection significantly increases the risk of its formation at a later age.
Which diseases require differential diagnosis of exanthema in manifest rubella in adults?
In adults with rubella, the rash is often abundant and may merge to form erythematous fields; sources indicate this as the reason for difficulties in differential diagnosis with:
- Measles.
- Scarlet fever.
The differential diagnosis section for rubella also indicates that the greatest difficulties arise in differential diagnosis with measles and parvovirus infection. For parvovirus infection in adults, a rash is less common or atypical, while arthritis is more frequent.
What is the management tactic for a pregnant woman and specific prophylaxis upon contact with a rubella patient in early gestation?
Upon contact of a pregnant woman with a rubella patient in early gestation, sources indicate the following tactics:
- Infection in the first trimester is a medical indication for pregnancy termination.
- A pregnant woman among contact persons is indicated for mandatory serological screening for rubella.
- In the presence of IgGs, the woman is considered immune.
- If antibodies are absent, a repeat test is performed in 4–5 weeks; if the repeat test is positive, pregnancy termination is offered, if negative — the next checkup is in a month.
Specific post-exposure prophylaxis:
- Administration of human immunoglobulin is generally not recommended.
- Exception: immunoglobulin is used only if the woman refuses pregnancy termination after contact/infection.
- Large doses are required for an effect, while protection is not guaranteed.
Remembering the classic CRS triad is helped by the acronym GGS: Eyes (cataracts), Deafness, Heart (congenital defects).
Class and exam questions
Why is asymptomatic rubella in pregnant women dangerous?
Hidden (inapparent) and atypical forms (without rash) occur in 20–30% of adults. A woman may not know she is ill, while the virus freely exerts a powerful teratogenic effect on the fetus.
Is it possible to establish a diagnosis in a pregnant woman based on rash alone?
No, the clinical picture is insufficient. In adults, exanthema can merge or be accompanied by hemorrhages, simulating other infections. The diagnosis must always be confirmed serologically (ELISA) or molecular-genetically (PCR).
What does the IgG avidity index indicate in suspected CRS?
It allows accurate determination of the timing of infection. An index below 30 confirms the acute stage and the presence of the virus in the body, while an index above 60 indicates a long-standing infection (presence of stable immunity).
What else to study on this topic
- Clinical picture of exanthema and enanthema (Forchheimer spots) in acquired rubella.
- Differential diagnosis of rubella with measles and erythema infectiosum (parvovirus).
- Specific complications in adults: acute arthritis and thrombocytopenic purpura.
- Changes in the hemogram in rubella (appearance of plasma cells).
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