Like in any other IVF procedure, after an embryo transfer with donated eggs, women have to go through the two-week wait or 2WW, a time period necessary for beta-hCG levels to be detectable by a pregnancy test.
The presence of the hormone hCG in blood increases gradually from embryo implantation up until the end of the third trimester approximately. This, along with other hormonal changes, is the reason why the common pregnancy symptoms appear (nausea, vomiting, etc.)