In general, when donor eggs have been used, pregnancy due date calculators work by adding two more weeks to the date of the embryo transfer. It allows us to copy the process followed in natural pregnancies, where we start counting from the first day of last menstrual period. In principle, embryo implantation occurs around 2-3 weeks before the last menstrual period.
By Andrea Rodrigo.
Last Update: 09/26/2016
Bachelor's Degree in Biotechnology from the Polytechnic University of Valencia. Master's Degree in Biotechnology of Human Assisted Reproduction from the University of Valencia along with the Valencian Infertility Institute (IVI). Postgraduate course in Medical Genetics.