Maternal Risk Factors for Congenital Cataract
The primary maternal risk factors for congenital cataract are infectious agents acquired during pregnancy, particularly toxoplasmosis, rubella, and herpes simplex virus, with the timing and treatment of maternal infection being critical determinants of fetal ocular damage.
Infectious Maternal Risk Factors
Toxoplasmosis
- Maternal primary toxoplasma infection during pregnancy carries the highest risk when occurring in early to mid-gestation, with chorioretinitis risk 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.
- Toxoplasma gondii IgM positivity was found in 8.3% of children with congenital cataract, with PCR positivity of 32.5% 2.
Rubella
- Maternal rubella infection in the first trimester is a major cause of congenital cataract, with any injury during the phase of organogenesis resulting in congenital rubella syndrome 3.
- Rubella virus showed IgM positivity in 5.8% of children with congenital cataract, with PCR positivity of 33.3% 2.
- The majority of rubella cases occur in young female immigrants, many coming for marriage, highlighting the importance of pre-pregnancy screening 3.
Herpes Simplex Virus
- Maternal HSV infection contributes to congenital cataract, with IgM positivity found in 1.6% and PCR positivity in 20.8% of affected children 2.
Zika Virus
- Maternal Zika virus infection during pregnancy is associated with congenital lens subluxation and other ocular abnormalities 4.
Geographic and Strain-Related Risk Factors
- The virulence of the infecting toxoplasma strain significantly impacts outcomes—in South America, type 1 and type 3 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.
Critical 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.
- Failure to immunize women before pregnancy against rubella remains a significant preventable risk factor 3, 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.
- Approximately 80% of infants with congenital toxoplasmosis are asymptomatic at birth, making maternal screening essential rather than relying on neonatal clinical findings 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.
- Fetal cataract can be detected prenatally on ultrasound in cases of congenital toxoplasmosis, which should inform prenatal counseling about long-term ocular sequelae 5.
Risk Stratification Algorithm
For toxoplasmosis:
- Highest risk: Maternal seroconversion before 20 weeks gestation + delayed treatment (>8 weeks) 1
- Moderate risk: Maternal seroconversion at 20-26 weeks gestation 1
- Lower risk: Maternal seroconversion after 26 weeks gestation, though still carries 10% symptomatic disease risk 1
For rubella: