All of the following statements about congenital rubella are true except ?

Increased risk of congenital malformation if infection occurs after 16 weeks Rubella Rubella is a teratogenic virus, can be transmitted from fetus to mother. The fetus is at risk for congenital rubella only during primary infection. The rate of transmission of rubella varies with gestational age. It is highly variable even during the first trimester. Rate of transmission of Rubella with gestational age First 4 postconception weeks 61% During weeks 5-8 decreases to 26% During weeks 9-12 decreases to 8% After 12 weeks The risk of congenital infection usually less than 5% Diagnosis of congenital rubella :? Congenital infection is considered to have occurred if the infant has IgM rubella antibodies sholy after bih or if IgG antibodies persists for more than six months by which time maternally derived antibodies would have disappeared. Fetal malformations not only are more common after maternal infection in the first trimester but also tend to be more severe and to involve more organ systems. Infection in the second trimester may cause deafness but those infected after 16 weeks suffer no major abnormality. The risk for congenital defects is related to the gestational age at the time of infection Gestational age Risk for congenital defects Before 11 weeks 90% 11-12 weeks 33% 13-14 weeks 11% 15-16 weeks 24% The most common abnormalities associated with first trimester infection are :- Hearinglosss --> 60-65% Eye defects --) 50-90% Hea disease ---). 40-85% Psychomotor retardation --) 25-40% Other uncommon abnormalities are:- Fetal and neonatal growth retardation Hepatosplenomegaly Thrombocytopenia,meningoencephalitis, Radiolucency of the long bones, myocardial necrosis. Rare abnormalities Microcephaly, brain calcifications Late onset features appearing after 3-12 months include Interstitial pneumonitis Chronic rubella like rash Recurrent infections Hypogammaglobulinemia Chronic diarrhoea Diabetes mellitus Progressive CNS deterioration Late sequale of Rubella Fifty percent of affected infants will attend schools for deafness and the deaf and 25% will require special schooling problems.