Hello i am pregnant i had sex on 16 th january 2016 my baby's due date is 21st october what i would like to know is wen exactly did i concieve? thank

January 16-20: It is very simple when a woman only has sex once. Fertilization can be about 10-100 hours after the sperm start swimming. That means January 16-20, no matter what else is happening, because that would be the time the woman has fertile sperm inside of her. In a natural pregnancy, there is no answer to "exactly" when conception happens... because nobody can ever know.