Infectious Diseases & Obstetrics & Family Medicine
Rubéole | Clinique Omicron Québec
Rubella—commonly called German measles or three-day measles, although it is caused by an entirely different virus than measles—is an acute viral infection caused by the rubella virus (Rubella virus), a positive-polarity, single-stranded RNA togavirus of the Matonaviridae family, transmitted directly from person to person by aerosol (respiratory droplets) or by mucous membrane contact with respiratory secretions from an infected person. In children and non-pregnant adults, rubella is a generally benign, self-limiting disease - characterized by a pale-pink, diffuse maculopapular exanthema + characteristic posterior cervical and sub-occipital lymphadenopathy + moderate fever + conjunctivitis + arthralgias (especially in adult women) - whose favorable evolution in 3 to 7 days requires only symptomatic treatment. Its major medical importance lies in its catastrophic teratogenicity when it occurs in a non-immune pregnant woman in early pregnancy: the virus crosses the placenta and infects the embryo during organogenesis, causing congenital rubella syndrome (CRS) - a devastating triad of congenital heart disease + cataracts + sensorineural deafness + mental retardation + retinopathy + microcephaly - with a risk of vertical transmission of over 90 % if infection occurs before the 12th week of amenorrhea (SA), and a risk of severe malformations exceeding 85 % in the first trimester. Thanks to systematic vaccination with the trivalent MMR (Measles-Mumps-Rubella) vaccine introduced in Quebec in 1970, and whose coverage is now very high (≥ 95 %), rubella and congenital rubella syndrome have been virtually eliminated in Canada - but remain a real threat for non-immune women (unvaccinated populations + certain immigrants from countries with low vaccination coverage) and for travellers to regions where rubella is still actively circulating.
Clinical presentation
- Incubation: 14 to 21 days (average 16–18 days) + infectious period: from 7 days before to 7 days after the onset of the rash → contagious BEFORE the rash = risk of transmission before diagnosis is suspected
- Prodromal phase (1–5 days): Posterior and suboccipital lymphadenopathy (almost pathognomonic early sign—present before rash) + mild fever (37.5–38.5 °C) + headache + rhinorrhea + pharyngitis + mild conjunctivitis + general malaise
- Rash (J0–J3 after prodrome): Pale pink maculopapular exanthem + starting on the face + spreading down to the trunk then limbs (craniocaudal progression) + lesions on the face may disappear by the time the rash reaches the lower limbs (rapid evolution in 3 days) + less confluent and paler than measles + possible pruritus + Forchheimer spots (small purpuric petechiae on the soft palate — present in 20% % of cases + non-specific)
- Joint pain and arthritis: very frequent in adult women (70 %) + especially the small joints of the hands and wrists + symmetrical + transient (a few days) + spontaneously regress without sequelae
- Asymptomatic forms 25 to 50 % of rubella infections are asymptomatic or have mild symptoms → possible contamination of a pregnant woman without the source being identified
- Rare complications: Thrombocytopenic purpura (1/3,000) + post-infectious encephalitis (1/6,000) + progressive rubella panencephalitis (very rare—late form similar to measles SSPE)
Rubella during pregnancy — risks by trimester
| Maternal infection term | Risk of transmission to the fetus | Risk of congenital malformations (RCM) |
|---|---|---|
| Before conception (periconceptional period) | Very low theoretical risk if infection occurred less than 4 weeks before conception | Minimal risk of SRC, but medical termination of pregnancy is not recommended on this criterion alone. |
| 1st trimester (< 12 weeks gestation) | 80–90 % of vertical transmission | > 85 % severe malformations (full SRC) → heart disease + cataracts + deafness + microcephaly + intellectual disability + abortion often offered |
| 13–16 SA | 54 % transmission | 10–25 % de malformations (principalement surdité isolée) → discussion au cas par cas + DPN par amniocentèse (PCR rubéole dans le liquide amniotique) |
| 17–22 SA | 25–35 % of transmission | Low risk of major structural malformations, but hearing loss, growth retardation, and a possible progressive syndrome after birth are possible. |
| After 22–23 weeks of gestation | 60–100 % of transmission (increases in late pregnancy) | Rare major malformations but risk of neonatal rubella (fever + rash + purpura + thrombocytopenia + hepatosplenomegaly at birth) |
Rubella serology — interpretation
| Serological result | Interpretation | Action to take |
|---|---|---|
| IgG positive + IgM negative | Old immunity (vaccination or past infection) + established immune protection | No risk for pregnancy → no additional measures + confirm vaccination in the record if in doubt |
| IgG negative + IgM negative | Lack of immunity → woman not protected against rubella | Outside of pregnancy: Vaccinate with MMR (2 doses) + During pregnancy: DO NOT vaccinate (live attenuated vaccine contraindicated during pregnancy) → isolation measures for subjects with infectious agents + mandatory vaccination immediately postpartum |
| IgG positive + IgM positive | Probable recent infection (IgM = marker of acute infection + appears from day 3-5 of rash) + or false positive IgM (possible in case of pregnancy + CMV infection + EBV + parvovirus B19) | Confirm by IgG avidity (low avidity = recent infection < 3 months + high avidity = old infection or vaccination) + if recent infection confirmed during pregnancy → urgent obstetrical-fetal discussion + ultrasound + amniocentesis + genetic counseling |
| IgG negative + IgM positive | Very recent infection (seroconversion ongoing — IgG not yet detectable) or false positive IgM | Repeat serology in 2-3 weeks. The appearance and increase in IgG will confirm seroconversion. Urgent management if pregnant. |
ℙ️
The rubella IgG avidity test is the key examination for dating a rubella infection when both IgG and IgM are positive – a common situation because IgM can remain detectable for weeks to months after an infection or vaccination. An avidity < 30–35 % indicates a recent infection ( 60–70 % indicates an old infection or vaccination = no immediate fetal risk. Avidity should be systematically requested during the assessment of a pregnant woman with positive IgM to avoid unnecessary interventions (termination of pregnancy) based on false positives.
Vaccination RRO - Quebec Program
- Quebec Vaccination Program: 1st dose MMR at 12 months + 2nd dose MMR-V (measles + rubella + mumps + varicella) at 18 months → vaccination coverage ≥ 95 % in Quebec + 2 doses confer lifelong immunity against rubella in > 99 % of cases
- Catch-up vaccination in adults: Anyone born after 1970 without proof of immunity (negative rubella IgG or incomplete vaccination record - less than 2 doses of MMR) → 2 doses of MMR 1 month apart. People born before 1970 are generally immune from natural infection (pre-vaccine era).
- Contraindications to MMR vaccine: Pregnancy (live attenuated vaccine) → effective contraception for 1 month after vaccination + severe immunosuppression (HIV with CD4 (200+ leukemia + chemotherapy + high-dose corticosteroids) + history of anaphylactic reaction to a previous dose
- Postpartum vaccination: Any pregnant woman who is not immune (IgG negative) should receive 1 dose of MMR immediately after delivery and before leaving the maternity ward. It is compatible with breastfeeding.
- Vaccination of health workers 2 doses of MMR documented are mandatory for all healthcare personnel in Quebec (MSSS) → systematic verification before taking up post
Obstetric emergency — rubella contact in pregnancy
An unvaccinated pregnant woman (rubella IgG-negative) who has had contact with a confirmed rubella case must consult her doctor or obstetrician urgently within 72 hours. A rubella serology (IgG, IgM, and avidity if IgM is positive) must be performed immediately and repeated in 2-3 weeks to confirm or rule out seroconversion. If infection is confirmed in the first trimester, an urgent discussion of prenatal diagnosis (amniocentesis + rubella PCR) and a fetal medicine consultation are essential. For screening of rubella immunity pre-conceptionally or early in pregnancy, Clinique Omicron offers medical consultations at its service points in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's physicians and nurse practitioners (NPs) check rubella immunity during preconception consultations and the first prenatal check-up, prescribe the MMR vaccine for non-immune women before pregnancy, screen unvaccinated women for immediate postpartum vaccination, interpret rubella serology (IgG + IgM + avidity), manage rubella contacts in pregnant women, and refer to obstetrics in emergencies if seroconversion is documented during pregnancy. Consultations are available at several service locations in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
The content of this page is provided for informational purposes only and does not substitute for medical advice from a doctor, obstetrician, or fetal medicine specialist. Any suspected rubella infection during pregnancy constitutes an obstetrical emergency requiring immediate specialized care. Rubella is a notifiable disease in Quebec.
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