The Orthodox Church negatively refers not to the procedure itself, but to the fact that several embryos are cultivated in the process, of which the most viable are selected, and the rest simply remove (read - kill). But after all, murder is a mortal sin, abortion along with murder is also considered a great sin. And the murder of a life that was hardly born, even in a test-tube, is undoubtedly also a sin.
IVF and Church
The way the church treats IVF is justified. As is known, the method of IVF consists of several stages. First, a woman is stimulated to produce several oocytes at the same time (superovulation). Sometimes it turns out 2, and sometimes all 20 eggs. After puncturing the mature eggs, they are placed in a special nutrient medium and connect them with the sperm of the husband. At this stage, it is still "legal" - no violation of morality occurred because the parents are married.
The resulting embryos are moved to the incubator for a while. And then after that comes the "moment X". Weak, non-viable embryos are removed, and the rest are planted by mothers. Sometimes embryos are frozen and stored for a long time.
Since 2-5 embryos are transferred into the uterus, the probability of multiple pregnancies is high. And if more than 2 embryos survived, the rest, as a rule, undergo reduction. They are not surgically removed, but by certain methods they achieve that they stop their development and eventually dissolve. This procedure is also equated with murder.
It is not surprising that the church opposes IVF. Artificial insemination and the church could coexist if doctors took only 1-2 eggs from a woman and after they fertilized them they re-inserted them. But no doctor will do this, as there are no guarantees that the operation will be successful. Without "spare" children, no medical center will act.