Hi, Thanks for posting in HCM. I understand your concern. Generally, a woman’s fertile window is the day of ovulation (usually 12 to 16 days before the menstrual period begins) and the five days preceding it, provided the period is regular with 28 days. Usually, the period occurs somewhere between days 10 and 17. Irrespective of on which day you have conceived, gestational age is calculated from the first day of the mother s last menstrual period, since the exact date of conception is almost never known. Hence, if you cannot correlate properly by taking last menstrual period, kindly take in to consideration the gestational age as suggested by ultrasound scan. The delivery might happen with +/- week from the given date as suggested by ultrasound scan. Take care to follow all the ante-natal instructions properly. Hope the information provided would be helpful. All the best.