bubble_chart Overview

If a pregnant woman contracts rubella in the early stages of pregnancy, the rubella virus can infect the fetus through the placenta. The newborn may be premature and may suffer from congenital heart defects, cataracts, deafness, developmental disorders, etc. This condition is known as congenital rubella or congenital rubella syndrome.

bubble_chart Etiology

The mechanism by which the rubella virus causes specific teratogenic effects remains incompletely understood. When a pregnant woman is infected with rubella, viremia occurs as early as one week before the eruption. Whether maternal rubella infection can be transmitted to the fetus depends on the timing of the maternal infection. Infection during the 2nd to 6th day-night cycles of embryonic development has the greatest impact on the heart and eyes. During the intermediate stage of pregnancy (second trimester), the fetus gradually develops immunity (such as the appearance of plasma cells and the production of IgM), making congenital rubella infection less likely to result in chronic infection compared to early pregnancy. According to observations by Kibrick et al. (1974), if a pregnant woman is infected with rubella during the first month of pregnancy, the incidence of congenital rubella syndrome in the fetus can be as high as 50%; in the second month, 30%; in the third month, 20%; and in the fourth month, 5%. It is also noted that infection with rubella after four months of pregnancy is not entirely without risk to the fetus.

bubble_chart Clinical Manifestations

Congenital rubella infection can result in late abortion, stillbirth, live births with malformations, or completely normal newborns, and it can also present as a latent infection. Almost all fetal organs may develop temporary, progressive, or permanent pathological changes.

1. Manifestations at birth: Live-born infants may exhibit some acute sexually transmitted disease changes, such as neonatal thrombocytopenic purpura, characterized by scattered purplish-red spots of varying sizes present at birth, often accompanied by other temporary lesions, poor calcification of the epiphyses of long bones, hepatosplenomegaly, hepatitis, hemolytic anemia, and a bulging anterior fontanelle. There may also be an increase in cerebrospinal fluid cells. These conditions represent severe manifestations of congenital infection. Other birth manifestations include low birth weight, congenital heart disease, white internal visual obstruction, deafness, and microcephaly, all of which have a poor prognosis. Based on a one-year follow-up of 58 infants with purpura, the mortality rate was as high as 35%. During the neonatal period, rubella viral hepatitis and interstitial pneumonia may also occur.
2. Cardiac malformations: The most common heart blood vessel anomalies include patent stirred pulse duct, with some cases even isolating rubella virus from the duct wall tissue. Pulmonary stirred pulse stenosis or branch stenosis is also relatively common, along with other defects such as atrial septal defect, ventricular septal defect, aortic arch abnormalities, and more complex malformations. Most infants do not exhibit severe heart blood vessel symptoms at birth; however, some may develop heart failure within the first month of life, which carries a poor prognosis.
3. Deafness: Hearing loss can range from mild to severe and may affect one or both ears. The pathology lies in the Corti's organ of the inner ear, though middle ear lesions may also occur. Deafness can also be the sole manifestation of congenital rubella, particularly in infections occurring after the 8th week of pregnancy.
4. Ocular defects: The most characteristic eye lesion is pear-shaped nuclear white internal visual obstruction, which is usually bilateral but can also be unilateral, often accompanied by microphthalmia. At birth, the white internal visual obstruction may be very small or invisible and must be carefully examined with an ophthalmoscope. Besides white internal visual obstruction, congenital rubella can also cause glaucoma, which is difficult to distinguish from hereditary infantile glaucoma. Congenital rubella glaucoma presents with enlarged and cloudy cornea, deepened anterior chamber, and increased intraocular pressure. Normal newborns may also have transient corneal cloudiness that resolves spontaneously and is unrelated to rubella. Congenital rubella glaucoma requires surgical intervention, whereas transient corneal cloudiness does not require treatment. The retina often shows scattered black pigment patches of varying sizes, which usually do not affect vision but aid in diagnosing congenital rubella.
5. Developmental disorders and neuro classical formula malformations: Intrauterine rubella infection can also affect the central nervous system. Autopsies of affected infants confirm that rubella virus has strong neurotoxicity, causing varying degrees of developmental defects. Cerebrospinal fluid often shows changes such as increased cell count and elevated protein concentration, and the virus may even be isolated from the cerebrospinal fluid up to one year of age.
6. Intellectual, behavioral, and motor developmental disorders are also hallmark features of congenital rubella. These early developmental impairments are due to rubella encephalitis and may result in permanent intellectual disability.

Generally, congenital heart malformations, white internal visual obstruction, and glaucoma are often caused by viral infection during the first 2–3 months of pregnancy, while deafness and central nervous system lesions are more likely due to infections later in pregnancy. Newborns may also exhibit transient congenital rubella manifestations, typically transmitted from early pregnancy infections, though occasionally from advanced stage pregnancy infections where both mother and fetus are affected simultaneously.

bubble_chart Auxiliary Examination

1. Virus isolation: Infants with congenital rubella can have chronic infections and continue to carry the virus for many months after birth, becoming a source of pestilence for contacts. Rubella virus can be isolated from the infant's throat secretions, urine, cerebrospinal fluid, and other organs, with higher isolation rates in cases of severe disease. In contrast, individuals with acquired rubella infections rarely shed the virus for more than 2–3 weeks. The positive rate of rubella virus isolation in congenital cases decreases with age and often becomes undetectable by the age of one. Unless the infant has a congenital immune deficiency and cannot produce antibodies, the virus is rarely isolated from the blood.
2. Serological testing: When a pregnant woman has a history of rubella exposure or clinical symptoms suggestive of rubella, serum rubella antibodies should be measured. If specific anti-rubella IgM is positive (using the ELA IgM test kit supplied by the Beijing Institute of Biological Products), it indicates a recent primary rubella infection, especially in early pregnancy, and consideration should be given to artificial late abortion. In infants with congenital rubella, the serum rubella antibody titer at birth is similar to that of the mother, primarily consisting of maternally transmitted IgG, which diminishes 2–3 months after birth. The infant's own anti-rubella IgM (which cannot cross the placenta) peaks at 3–4 months of age and disappears by around one year. The infant's own anti-rubella IgM begins to rise within the first month after birth, peaks at one year, and may persist for several years. Therefore, if rubella-specific IgM is detected in the serum of a newborn or if rubella IgM antibodies remain significantly elevated 5–6 months after birth without postnatal infection, it confirms congenital rubella. As mentioned earlier, individuals with acquired rubella infections retain hemagglutination inhibition antibodies for life, whereas about 20% of congenital rubella patients lose detectable antibodies by age five. Generally, 95% of susceptible children produce antibodies after rubella vaccination, whereas congenital rubella patients whose antibodies have waned rarely respond to vaccination. Thus, if a child over three years old fails to produce detectable hemagglutination inhibition antibodies after rubella vaccination—after excluding immunodeficiency and other causes—the diagnosis of congenital rubella can be supported by the mother's history of rubella infection during pregnancy and the child's clinical manifestations.

bubble_chart Diagnosis

1. Epidemiological data: The pregnant woman had a history of rubella exposure or onset during the pregnancy initial stage [first stage], and laboratory tests have confirmed maternal rubella infection.
2. The newborn exhibits one or several manifestations of congenital defects.
3. Specific rubella IgM antibodies are present in serum or cerebrospinal fluid samples during early infancy.
4. When passively acquired maternal antibodies are no longer detectable 8–12 months after birth, the child continues to show persistent rubella antibodies at significant levels in consecutive serum samples.

bubble_chart Treatment Measures

The treatment for congenital rubella syndrome is only symptomatic, and care should be provided by individuals with rubella antibodies. After discharge, contact with pregnant women must be avoided.

bubble_chart Prevention

Methods for preventing congenital rubella syndrome, refer to the prevention of rubella mentioned above. It is noteworthy that rubella reinfection during pregnancy can still affect the fetus. Among pregnant women who have been vaccinated against rubella, the chance of reinfection is much higher than in those who have naturally contracted rubella. During pregnancy, the increase in adrenal corticosteroids in the body and the reduction in cellular immune function make it easier for the virus to spread within the body, thereby affecting the fetus.

For non-pregnant individuals, rubella reinfection is almost always asymptomatic, without viremia, and merely acts like a vaccine booster, increasing antibody levels in the body. However, in pregnant women, reinfection can potentially lead to congenital rubella syndrome. Therefore, even if a pregnant woman has been vaccinated against rubella, it is equally important to strictly isolate her from rubella patients.