Live birth rate

Pregnancy rate is the success rate for getting pregnant. It is the percentage of all attempts that leads to pregnancy, with attempts generally referring to menstrual cycles where insemination or any artificial equivalent is used, which may be simple artificial insemination (AI) or AI with additional in vitro fertilization.

There is no universally accepted definition of the term. Thus in IVF pregnancy rates may be based on initiated treatment cycles, cycles that underwent oocyte retrieval, or cycles where an embryo transfer was performed. In terms of outcome, "pregnancy" may refer to a positive pregnancy test, evidence of a pregnancy with a "viable" fetus or implantation. Furthermore, pregnancy rates can be influenced in IVF by transferring multiple embryos that may result in multiple births. A strict definition in the IVF setting would refer to the singleton pregnancy rate that determines how many live singletons are born in relation to initiated IVF cycles.

In some cases, success rates include delivery or presence of a live baby (preferably specified as delivery rate or live birth rate respectively).

Implantation rate is the percentage of embryos which successfully undergo implantation compared to the number of embryos transferred in a given period. In practice, it is generally calculated as the number of intrauterine gestational sacs observed by transvaginal ultrasonography divided by the number of transferred embryos. As an example, one center in the United States reported an implantation rate in IVF of 37% at a maternal age of less than 35 years, 30% at 35 to 37 years, 22% at 38 to 40 years, and 12% at 41 to 42 years.

Successful implantation of the zygote into the uterus is most likely 8 to 10 days after conception. If the zygote has not implanted by day 10, implantation becomes increasingly unlikely in subsequent days.

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Wikipedia