This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Virology (RNA Virus Pa-1,2 & Miscellaneous Viruses), Subject name: Microbiology
Risk of rubella to fetus is maximum, if the mother is infected in: 
Select and explain. 
A. 6-12 weeks, B. 20-24 weeks, C. 24-28 weeks, D. 32-36 weeks
A: 6-12 weeks
Answer: A: 6-12 weeks 
Explanation: Risk of rubella to fetus is maximum, if the mother is infected in 6-12 weeks. Timing of fetal infection determines the extent of teratogenic effect in fetus Ist 2 months Abnormalities in 65-85% cases, Multiple congenital defects (cataracts, deafness and hea defects) Spontaneous aboion 3rd month of fetal life: 30% to 35% chance of developing a single defect, Deafness ,CHD. During the 4th month 10% risk for a single congenital defect Beyond the 4th month No risk to fetus