Blastocyst transfer ameliorates live birth rate compared with cleavage-stage embryos transfer in fresh in vitro fertilization or intracytoplasmic sperm injection cycles: reviews and meta-analysis

Abstract

Purpose: Blastocyst transfer has been recommended to raise the implantation rate without affecting the pregnancy rate. The objective of this meta-analysis is to systematically evaluate whether the live birth rate and other pregnancy outcomes can be improved by blastocyst transfer compared with cleavage-stage embryos transfer.

Materials and methods: EMBASE and MEDLINE databases were searched for papers published between March 2004 and March 2013. An extensive range of the electronic databases yielded initially 317 studies from which seven trials met the inclusion criteria for further analysis. Our outcome measures were the live birth rate, clinical pregnancy rate, implantation rate, ongoing pregnancy rate, multiple pregnancy rate, first trimester miscarriage rate and ectopic pregnancy rate. Fixed effects models were chosen to calculate the odds ratio (OR).

Results: Seven trials (n=1446 cases) were finally analyzed. Compared with cleavage-stage embryos transfer, the blastocyst transfer was statistically significantly associated with an increase in clinical pregnancy rate [OR 1.43; 95% confidence interval (CI), 1.15-1.78], implantation rate (OR 1.38; 95% CI, 1.09-1.74) and ongoing pregnancy rate (OR 2.15; 95% CI, 1.57-2.94), and also a reduction in the probability of first trimester miscarriage rate (OR 0.51; 95% CI, 0.30-0.87). The improvement in the live birth rate was also observed (OR 1.77; 95% CI, 1.32-2.37). Moreover, there was no evidence of difference in multiple pregnancy and ectopic pregnancy rates.

Conclusion: The available evidences suggest that live birth and other pregnancy outcomes after fresh in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) are significantly improved following blastocyst transfer as compared to cleavage-stage embryo transfer.

Keywords: Blastocyst; cleavage stage; embryo transfer; live birth rate; meta-analysis.

Fig. 1

Flow diagram of the systematic review and meta-analysis.

Fig. 2

Forest plot of comparison: live birth rate per couple. The horizontal bars extending to the right and left of the black circles represent the widths of 95% confidence intervals (CIs). The variation in the CIs is a function of different sizes of the samples. M-H, Mantel-Haenszel.

Fig. 3

Forest plot of comparison: clinical pregnancy rate per couple. The horizontal bars extending to the right and left of the black circles represent the widths of 95% confidence intervals (CIs). The variation in the CIs is a function of different sizes of the samples. M-H, Mantel-Haenszel.

Fig. 4

Forest plot of comparison: implantation rate per embryo transfer. The horizontal bars extending to the right and left of the black circles represent the widths of 95% confidence intervals (CIs). The variation in the CIs is a function of different sizes of the samples. M-H, Mantel-Haenszel.

Fig. 5

Forest plot of comparison: ongoing pregnancy rate per couple. The horizontal bars extending to the right and left of the black circles represent the widths of 95% confidence intervals (CIs). The variation in the CIs is a function of different sizes of the samples. M-H, Mantel-Haenszel.

Fig. 6

Forest plot of comparison: multiple pregnancy rate per clinical pregnancy. The horizontal bars extending to the right and left of the black circles represent the widths of 95% confidence intervals (CIs). The variation in the CIs is a function of different sizes of the samples. M-H, Mantel-Haenszel.

Fig. 7

Forest plot of comparison: first trimester miscarriage rate. The horizontal bars extending to the right and left of the black circles represent the widths of 95% confidence intervals (CIs). The variation in the CIs is a function of different sizes of the samples. M-H, Mantel-Haenszel.

Fig. 8

Forest plot of comparison: ectopic pregnancy rate. The horizontal bars extending to the right and left of the black circles represent the widths of 95% confidence intervals (CIs). The variation in the CIs is a function of different sizes of the samples. M-H, Mantel-Haenszel.