Abstract
BackgroundIn patients with low numbers of embryos, there is not yet consensus on whether to extend culture to the blastocyst stage, especially due to the risk that some or all of the embryos will not make it to the blastocyst stage. The objective of our study was to evaluate pregnancy outcomes in patients with a low number of fertilized oocytes (< 4), comparing single blastocyst transfer to one or more cleavage embryo transfer.ResultsWe analyzed 6795 cycles from the 2014–2105 Society for Assisted Reproductive Technology (SART) registry. All patients were ≤ 38 years old, had less than four fertilized oocytes, and were undergoing first fresh in vitro fertilization (IVF) transfer. Primary outcomes were clinical pregnancy (CP), live birth (LB), and miscarriage rate in both cleavage stage transfer and single blastocyst transfer. A secondary outcome was the rate of twin gestation. The comparison of interest in day of transfer included (1) single blastocyst vs single cleavage and (2) single blastocyst vs multiple cleavage stage. The association between day of transfer and primary outcome was investigated using logistic regression, controlling for the age, race/ethnicity, BMI, smoking, gravidity, parity, infertility diagnoses, and assisted hatching.Single blastocyst transfer was associated with an increased odds of CP (adjusted OR 2.03) and LB (adjusted OR 1.86) when compared to single cleavage transfer, and no statistically significant association was observed when comparing single blastocyst transfer to multiple cleavage embryo transfer for CP (adjusted OR 0.94) and LB (adjusted OR = 0.88). The odds of having twins among single blastocyst transfer was significantly lower compared to those odds that among multiple cleavage stage transfer (unadjusted OR 0.09).ConclusionsWhile pregnancy outcomes are similar between single blastocyst and multiple cleavage embryo transfer, the twin rate is reduced significantly among the single blastocyst transfers in patients with a low number of fertilized oocytes.
Highlights
In patients with low numbers of embryos, there is not yet consensus on whether to extend culture to the blastocyst stage, especially due to the risk that some or all of the embryos will not make it to the blastocyst stage
In our respective cohort study, we found that pregnancy outcomes (CP, live birth (LB)) are significantly improved with single blastocyst transfer compared to single cleavage embryo transfer and similar compared to multiple cleavage transfer in patients with < 4 fertilized oocytes
We found that the twin rate is significantly lower with a single blastocyst transfer compared to multiple cleavage stage transfer, decreasing pregnancy complications
Summary
In patients with low numbers of embryos, there is not yet consensus on whether to extend culture to the blastocyst stage, especially due to the risk that some or all of the embryos will not make it to the blastocyst stage. The objective of our study was to evaluate pregnancy outcomes in patients with a low number of fertilized oocytes (< 4), comparing single blastocyst transfer to one or more cleavage embryo transfer. In the current era of in vitro fertilization (IVF), many practitioners choose to extend embryo culture to the blastocyst stage as blastocyst transfers have shown an association of an improved clinical pregnancy (CP) rate and live birth (LB) rate [1]. In a randomized control trial by Papanikolaou et al in patients under age 36, higher clinical pregnancy and live birth rates were seen with a single blastocyst compared to a single cleavage stage transfer [3]. With blastocyst transfer, there is a decreased risk of multiple gestation as less embryos can be transferred with a similar live birth rate. A single blastocyst transfer is the preferred method of transfer, as it leads to improved pregnancy rates and a reduced risk of multiple gestation
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