Congenital Rubella Syndrome

Congenital rubella syndrome (CRS) results from transplacental infection of the fetus by rubella virus (a togavirus) during pregnancy.

The risk of fetal infection and defects depends on gestational age:

• up to 90% for infection before 11 weeks
• about 50% at 11 to 12 weeks
• 30% at 13 to 14 weeks
• 10 to 20% at 15 to 16 weeks
• defects rare after 20 weeks (though deafness can occur up to 20 weeks)

Where vaccination is effective (MMR), CRS is eliminated. It persists in countries without universal rubella immunisation, with an estimated 100,000 cases per year worldwide historically. Maternal reinfection is rarely a risk. Infected infants shed virus in pharyngeal secretions and urine for up to 1 year.

Classic triad: sensorineural deafness (most common single defect, about 60 to 90%), cardiac defects (patent ductus arteriosus and peripheral pulmonary artery stenosis), and ocular defects (cataract, retinopathy with salt-and-pepper pigmentary change, glaucoma, microphthalmia). Other features:

• Neonatal: low birth weight, hepatosplenomegaly, thrombocytopenic purpura ("blueberry muffin" rash from dermal erythropoiesis), jaundice, meningoencephalitis, bone lucencies (celery stalk metaphyses), interstitial pneumonitis
• Neurological: microcephaly, developmental delay, intellectual disability, behavioural disorder, autism features, and progressive rubella panencephalitis (rare, in the second decade)
• Delayed manifestations: type 1 diabetes mellitus (up to 20% by adulthood), thyroid disease (hypothyroidism, thyroiditis), precocious puberty or growth hormone deficiency, hypertension from renal artery stenosis, and late hearing and visual deterioration

1. Rubella specific IgM antibody in the infant's serum (positive in 100% by 1 month of age but may be negative later; collect at birth to 6 months) or persistent rubella specific IgG beyond 6 to 12 months (as maternal antibody wanes).
2. Rubella virus detection by RT-PCR on throat swab, nasopharyngeal aspirate, urine, or CSF (positive for months), and virus isolation in culture.
3. Maternal diagnosis during pregnancy: rubella IgM and IgG avidity (low avidity suggests recent infection), with fetal diagnosis by PCR on amniotic fluid or chorionic villus sample.
4. Evaluate infants: ophthalmological examination, audiological testing (auditory brainstem response), echocardiography, cranial ultrasound or MRI, blood count, liver function, TSH, and developmental assessment.
5. Case definition by clinical criteria plus laboratory confirmation.

There is no antiviral therapy. Care is supportive and multidisciplinary.

• Infection control: isolate infants with CRS and treat them as infectious until 1 year of age, or until 2 negative cultures at least 1 month apart; avoid contact with pregnant women and susceptible patients.
• Hearing: early hearing aids and cochlear implantation, language intervention, and annual audiology.
• Cardiac: surgical ligation or catheter closure of PDA; balloon angioplasty or stenting of pulmonary artery stenosis.
• Eye: cataract surgery (early, with aphakic correction), glaucoma treatment, and annual ophthalmology (retinopathy rarely affects vision).
• Neurological and developmental: early intervention, special education, and anticonvulsants for seizures.
• Endocrine surveillance: HbA1c or fasting glucose and TSH annually from school age.
• Prevention: rubella vaccination (MMR; first dose at 12 to 15 months, second dose at 4 to 6 years, or MR vaccine 9 to 12 months in endemic countries).
• Check rubella immunity before pregnancy and vaccinate non-immune women at least 4 weeks before conception. MMR is contraindicated in pregnancy. Vaccinate non-immune women post-partum.
• For exposure in pregnancy, arrange urgent rubella IgG testing; immune globulin is not reliable.
• Management of infection in the first 16 weeks involves counselling regarding termination and fetal diagnosis.
• Surveillance and notification of cases to public health authorities.