i had my period on the 8th of feb. and conceived on the 28th of feb. i am absolutely sure this is the day i conceived because my husband had been out of town on business, came home for a long weekend, and left again for work. i was not planning this pregnancy, although we are very happy, so i am scared that i was not taking multivitamins or folic acid...i am now. i guess my questions is, do i calculate how old the fetus is by the day of conception...which would be better because it wouldn't be as far developed...or the day my period began, which is three weeks before we concieved...making us 6 weeks which scares be since like i said, i wasn't taking folic acid. grrrr, it is driving me nuts trying to figure out how to caculate this...