Gestational age and pregnancy dating after IVF

After IVF, gestational age is calculated from the date of egg collection (fertilisation age) plus two weeks, or from the transfer date adjusted for the embryo's age (day 3 or day 5/6 blastocyst). This is more accurate than counting from the last menstrual period, because the exact date of fertilisation is known. Your clinic will usually give you an estimated due date at the time of transfer and confirm it again at the first ultrasound scan, once a gestational sac, yolk sac and, later, cardiac activity are visible. Small differences of a few days between calculated and scan dating are common and not usually a cause for concern.

Also known as: IVF due date, pregnancy dating, gestational age after IVF, how many weeks after IVF

Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.