Cleavage stage versus blastocyst stage embryo transfer in assisted conception

Blake D, Farquhar C, Johnson N, Proctor M

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Summary

Cleavage stage versus blastocyst stage embryo transfer in assisted conception

Keeping embryos a few days longer in the laboratory before transfer has not been shown to lead to more pregnancies than regular IVF
In vitro fertilisation (IVF) is fertilisation (egg and sperm creating an embryo) in a laboratory (in a 'test tube'). With regular IVF, embryos are transferred into the woman's uterus two to three days after fertilisation (at the cleavage stage). An alternative technique delays transferal until five to six days after fertilisation (at blastocyst stage). This may be better timing and allow choice of more viable embryos. The review of trials found evidence that more women will have a pregnancy and baby with blastocyst transfer than with regular IVF. There was however, a higher risk that a women would have fewer embryos to freeze and no embryos available for transfer.

This is a Cochrane review abstract and plain language summary, prepared and maintained by The Cochrane Collaboration, currently published in The Cochrane Database of Systematic Reviews 2010 Issue 1, Copyright © 2010 The Cochrane Collaboration. Published by John Wiley and Sons, Ltd.. The full text of the review is available in The Cochrane Library (ISSN 1464-780X).
This record should be cited as: Blake D, Farquhar C, Johnson N, Proctor M. Cleavage stage versus blastocyst stage embryo transfer in assisted conception. Cochrane Database of Systematic Reviews 2007, Issue 4. Art. No.: CD002118. DOI: 10.1002/14651858.CD002118.pub3.

This version first published online: April 22. 2002
Last assessed as up-to-date: July 23. 2007

Abstract

Background

Recent advances in cell culture media have led to a shift in IVF practice from early cleavage embryo transfer to blastocyst stage transfer. The rationale for blastocyst culture is to improve both uterine and embryonic synchronicity and self selection of viable embryos thus resulting in higher implantation rates.

Objectives

To determine if blastocyst stage embryo transfers (ETs) affect live birth rate and associated outcomes compared with cleavage stage ETs and to investigate what factors may influence this.

Search strategy

Cochrane Menstrual Disorders and Subfertility Group Specialised Register of controlled trials, Cochrane Controlled Trials Register (CENTRAL) (The Cochrane Library), MEDLINE, EMBASE and Bio extracts. The last search date was January 2007.

Selection criteria

Trials were included if they were randomised and compared the effectiveness of early cleavage versus blastocyst stage transfers.

Data collection and analysis

Of the 50 trials that were identified, 18 randomised controlled trials (RCTs) met the inclusion criteria and were reviewed. The primary outcome was rate of live birth. Secondary outcomes were rates per couple of clinical pregnancy, multiple pregnancy, high order pregnancy, miscarriage, failure to transfer embryos and cryopreservation. Quality assessment, data extraction and meta-analysis were performed following Cochrane guidelines.

Main results

Evidence of a significant difference in live-birth rate per couple between the two treatment groups was detected in favour of blastocyst culture (9 RCTs; OR 1.35, 95% CI 1.05 to 1.74 (Day 2/3: 29.4% versus Day 5/6: 36.0%)). This was particularly for trials with good prognosis patients, equal number of embryos transferred (including single embryo transfer) and those in which the randomisation took place on Day 3. Rates of embryo freezing per couple was significantly higher in Day 2 to 3 transfers (9 RCTs; OR 0.45, 95% CI 0.36 to 0.56). Failure to transfer any embryos per couple was significantly higher in the Day 5 to 6 group (16 RCTs; OR 2.85, 95% CI 1.97 to 4.11 (Day 2/3: 2.8% versus Day 5/6: 8.9%)) but was not significantly different for good prognosis patients (9 RCTs; OR 1.50, 95% CI 0.79 to 2.84).

Authors' conclusions

This review provides evidence that there is a significant difference in pregnancy and live birth rates in favour of blastocyst transfer with good prognosis patients with high numbers of eight-cell embryos on Day three being the most favoured in subgroup for whom there is no difference in cycle cancellation. There is emerging evidence to suggest that in selected patients, blastocyst culture maybe applicable for single embryo transfer.

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