Some things we have read say that the
third trimester begins at the START of the seventh month-
week 25. Some things we have read say that it starts at the END of the seventh month-week 28. I can't remember from my first pregnancy if it is the 2nd trimester that is 4 months or the 3rd trimester. I'll ask my doctor tomorrow what he considers the start of the third but I was just curious what anyone on this site thinks.