COMMENTARY

Top Assisted Reproductive Technology Literature From 2014

Peter Kovacs, MD, PhD

Disclosures

December 18, 2014

In This Article

Measures of IVF Success

Number of Embryos Transferred After In Vitro Fertilization and Good Perinatal Outcome
Kissin DM, Kulkarni AD, Kushnir VA, Jamieson DJ; National ART Surveillance System Group
Obstet Gynecol. 2014;123 (2 Pt 1):239-247

Success during in vitro fertilization (IVF) can be measured by multiple outcome parameters. Earlier studies tended to use surrogate markers of success such as oocyte yield, embryo availability, and number of good-quality embryos or implantation and pregnancy rates. More recently, ongoing pregnancy or live birth rates have been used. Even these outcome parameters are not adequate when keeping in mind the goal of a delivery of a healthy, full-term child.

In their analysis, Kissin and colleagues used the National Assisted Reproductive Technology Surveillance System database to study the association between good perinatal outcome and the number of embryos transferred. Good perinatal outcome was defined as live birth of a singleton weighing over 2500 g after 37 weeks of gestation. Patients were grouped according to their prognosis during IVF. Good-prognosis patients were those who underwent their first treatment and had surplus embryos for cryopreservation. Patients were considered to have poor prognosis when they underwent a repeat treatment, had no previous live births, and had no embryos available for cryopreservation. Patients who underwent their first cycle but had no extra embryos to freeze, those who had no previous live births but had available embryos to freeze, and those undergoing a repeat IVF treatment but had previous live birth were considered to have an average prognosis.

Data based on 82,508 IVF cycles that had reached the stage of embryo transfer using the patient's own oocytes were considered for the analysis. Forty-four percent of the cycles were performed in women under 35 years, and a single embryo was transferred in less than 20% of the cycles.

Among patients under 35 with good prognosis, the chance for good perinatal outcome was higher following the transfer of a single embryo (both with day 3 and day 5 transfers). Among women between the ages of 35 and 37 with good prognosis, the chance for good perinatal outcome was higher when a single blastocyst was transferred on day 5. In older patients with favorable prognosis, there was no statistically significant association between the chance of good perinatal outcome and the number of embryos transferred.

In patients under 35 with average prognosis, the chance of good perinatal outcome was higher following the transfer of a single blastocyst on day 5. The chance for good perinatal outcome was better after the transfer of two embryos in women under 35, 35-37, and 38-40 years of age when the transfer took place on day 3 at the cleavage stage.

In women under 35 with a poor prognosis, the chance for good perinatal outcome was higher with the transfer of two day 3, cleavage-stage embryos. In other age groups, no significant association was found between good perinatal outcome and the number of embryos transferred.

The authors calculated how much money could have been saved by avoiding preterm deliveries with the elective transfer of a single embryo only in women under 35 with good prognosis. They calculated that close to three fourths of the preterm deliveries could have been avoided (12.2% instead of the actual 37.2%). Using the published average cost associated with the care of a preterm newborn, over $177 million could have been saved.

Viewpoint

The need for optimal perinatal outcome has to be taken into consideration when recommendations are made on the number of embryos transferred. There are countries where the elective transfer of a single embryo is mandatory based on certain age restrictions. According to the results of this study, we can conclude that the transfer of a single embryo is optimal in women under 35 with good and average prognosis and in women between 35 and 37 with good prognosis. Among patients with less favorable prognosis or among older patients, the transfer of two embryos seems to result in optimal outcome. The important question is how to identify the single embryo with the highest implantation potential.

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