What are the maternal risk factors for congenital cataract?

Maternal Risk Factors for Congenital Cataract

The most critical maternal risk factor for congenital cataract is primary infection with specific pathogens during pregnancy, particularly rubella virus in the first trimester, toxoplasmosis (especially before 20 weeks gestation), and herpes simplex virus. 1, 2, 3

Infectious Maternal Risk Factors

Toxoplasmosis

• Maternal primary toxoplasma infection (seroconversion) during pregnancy carries the highest risk when occurring in early to mid-gestation, with the risk of chorioretinitis being 2.1 times higher if maternal infection occurs before 20 weeks compared to after 20 weeks. 1
• The timing of maternal seroconversion directly impacts severity—at 13 weeks gestation, there is a 61% risk of symptomatic congenital toxoplasmosis, decreasing to 25% at 26 weeks and 9% at 36 weeks. 1
• Delayed maternal treatment (>8 weeks after seroconversion) significantly increases the risk of ocular disease in the infant (HR: 2.54; 95% CI: 1.14-5.65). 1
• The risk of chorioretinitis decreases by 3% for each additional week of gestation when maternal infection occurs (OR: 0.97; 95% CI: 0.93-1.00 per week). 1

Rubella Virus

• Maternal rubella infection during the first trimester is a critical cause of congenital cataract, occurring during the phase of organogenesis and resulting in congenital rubella syndrome. 2
• Rubella virus was found to be IgM positive in 5.8% of children with congenital cataract, with PCR positivity of 33.3% in one tertiary care study. 3
• The majority of rubella cases occur in young female immigrants who lack immunity, highlighting the importance of pre-pregnancy screening and vaccination. 2

Herpes Simplex Virus

• Maternal HSV infection contributes to congenital cataract with IgM positivity of 1.6% and PCR positivity of 20.8% in affected children. 3

Toxoplasma gondii

• Beyond the timing factors mentioned above, T. gondii showed IgM positivity of 8.3% and PCR positivity of 32.5% in children with congenital cataract. 3

Geographic and Strain-Related Risk Factors

• The virulence of the infecting organism strain significantly impacts outcomes—in South America, type 1 and type 3 toxoplasma strains predominate (versus less virulent type 2 in Europe), resulting in more severe ocular disease. 1
• In North America, all three main toxoplasma types (1,2, and 3) are encountered, plus more virulent type 12 strains. 1

Modifiable Maternal Risk Factors

• Lack of antepartum screening and treatment programs represents a major preventable risk factor—the absence of routine screening in the United States and South America explains higher rates of severe congenital toxoplasmosis compared to European countries with screening programs. 1
• Maternal immune status prior to pregnancy is critical—susceptible women should be identified and vaccinated before conception for rubella. 2

Clinical Pitfalls to Avoid

• Do not assume that later gestational infections are benign—while earlier infections cause more severe disease, toxoplasmosis acquired at 26 weeks still carries a 10% risk of symptomatic congenital disease. 1
• The cumulative risk of eye disease increases over time—from 10% in early infancy to 30% by 12 years of age—so initial absence of cataract does not exclude future development. 1
• Approximately 80% of infants with congenital toxoplasmosis are asymptomatic at birth, making maternal screening essential rather than relying on neonatal clinical findings. 1