No, pregnancy rates do not increase with the number of embryo transfers. In general, pregnancy rates per transfer in IVF/ICSI cycles are 60% (depending on the age of the patient) with a cumulative pregnancy rate of 90% on the fourth attempt. This does not mean that in the fourth attempt there is a 90% pregnancy rate, but rather that, of all the patients/couples that do IVF/ICSI cycles, 90% of them achieve pregnancy in the fourth attempt, considering that, per attempt, it is 60%.
Similarly, in cycles with donated eggs, pregnancy rates can be 70% with a cumulative pregnancy rate of 99% in a fourth attempt.
It is important to note that, if after a second transfer of good quality embryos pregnancy is not achieved, we must perform a study to determine the cause of the failure (Implantation Failure, etc).