<prompt> Maximum teratogenic effect on heart of fetus is between-2-4 weeks4 - 6 weeks6 - 8 weeks8-10 weeks  <response>: Ans. is c i.e., 6-8 weeks Period of gestation and teratogenso Based on the gestation at exposure, a teratogen can either induce an embryopathy or a fetopathy.o From this perspective several critical periods of embryonic or fetal development are described:Preimplantation - fertilization to implantationEmbryonic - second through the ninth weekFetal - ninth week to termo Period of orsanosenesis Embryonic -2-8 weeks of conception is the time of maximum vulnerability, and each embryonic system has a period of maximum susceptibility. Heart is typically affected if the teratogen acts between 6-8 weeks of gestation. CNS maximum susceptibility between 17 - 30th post fertilization days. 