The 28th day of IVF transfer falls in the 6 to 7 week range, and the exact algorithm for how many weeks of IVF is needed to be determined based on the period of the embryo that was transferred. If the mother transfers an embryo that is a day 3 embryo, the calculation of the gestational week of pregnancy should be pushed forward 17 days, and the calculation of the gestational week is 28 days plus 17 days from the time of transfer. If the mother transfers a day 5-6 embryo, the gestational week is calculated 20 days ahead, and the gestational week is calculated as 28 days plus 20 days at the time of transfer. Conception under normal circumstances is usually calculated from the first day of the last menstrual period to the time of conception. Usually the same as the ultrasound projection. Consult a medical professional for advice.