am 2-3 weeks pregnant so in fact im 4-5 weeks and the baby is due in December. Is this correct? Surely my cycle would have changed due to my miscarriage and longer period. I am slightly confused. Does any one know? anadd said on 19 March 2012 Expecting87 all i know is count from the first day of your last period but you are actually conceived after your period when it was due ovulation. so it should minus 2 weeks. does it make sense? because it dose not mean you conceived on the first day or your period, it just start counting from it but when you conceived, it should be in later day after you finish your period and near ovulation where the eggs release. Expecting87 said on 18 March 2012 Hi I had my first scan this week at which I was told my due date is 17th September and I'm over 13 weeks gone! How is this calculated I have read lots of eyesores saying its taken from first day of last period which would make my last period 12th December which seems about right to me but have never been regular so can't remember exactly. My issue is that the first time I slept with my partner was 11 weeks ago Monday 26th December which is 14days after the day yey are dating my pregnancy from Is this right? Just need some reassurance because obviously my partner is thinking hang on that's before we did anything!?