<prompt> Highest transmission of hepatitis B from mother to fetus occurs, if the mother is infected during:1st trimesterIInd trimesterIIIrd trimesterAt the time of implantation  <response>: The virus is transmitted by parenteral route, sexual contact, veical transmission and rarely breast milk. The risk of transmission to fetus ranges from 10 in 1st TM to as high as 90 in 3rd TM. It is specifically high 90 from those mothers who are seropositive to hepatitis B surface AntigenHBsAg and e-antigenHBeAg Reference: Textbook of Dutta,9th edition, page 271 