CLEAVAGE VS BLASTOCYST

STAGE EMBRYO TRANSFER

2013, Issue 6

Description of the Intervention

Over the past decade there has been a steady shift in practice to

transfer of embryos on Day 5 or 6 when the embryos are

‘blastocysts’, the 64-cell stage.

The need for an evidence-based approach using meta-analysis of

small trials was, therefore, required to assist in deciphering the

overall effect of blastocyst culture to help identify patient

subsets and practices that might best benefit from this approach.

With the application of stage-specific media, there have been

reports of blastocyst development and implantation rates as

high as 60% to 65% (Shoolcraft 2001).

The uterus provides a different nutritional environment from

the oviduct; therefore it is postulated that this may cause stress

on the embryo and result in reduced implantation potential

(Gardner 1996).

The second argument for blastocyst culture is their innately

higher implantation potential compared with early cleavage

embryos. As a consequence of self selection, it is postulated

that only the most viable embryos are expected to develop into

blastocysts.

ARGUMENTS FOR BLASTOCYST TRANSFER

Objectives

To determine if blastocyst stage (Day 5 to 6) embryos transfers (Ets) improve

live birth rate and other associated outcomes compared with cleavage stage

(Day 2 to 3) Ets.

Data Collection and analysis

Of the 50 trials that were identified, 23 randomised controlled trials (RCTs)

met the inclusion criteria and were reviewed (five new studies were added in

this update). The primary outcome was rate of live birth. Secondary

outcomes were rates per couple of clinical pregnancy, cumulative 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.

Results

There was no difference in clinical pregnancy rate

between early cleavage and blastocyst transfer in the

23 RCTs and no difference in miscarriage rate (13

RCTs).

Embryo freezing rates (11 RCTs, 1729 women) and

failure to transfer embryos (16 RCTs, 2459 women)

favoured cleavage stage transfer.

Authors’ conclusions

This review provides evidence that there is a small significant

difference in live birth rates in favour of blastocyst transfer (Day 5 to 6)

compared to cleavage stage transfer (Day 2 to 3). However, cumulative

clinical pregnancy rates from cleavage stage (derived from fresh and

thaw cycles) resulted in higher clinical pregnancy rate than from

blastocyst cycles.

Future RCTs should report miscarriage, live birth and cumulative live

birth rates to enable ART consumers and service providers to make well

informed decisions on the best treatment option available.

WHAT IS THE CHANCE OF A DAY 3 EMBRYO

MAKING IT TO BLASTOCYST STAGE?

GOOD AND POOR AT CLEAVAGE STAGE

Overall Rates for Good or Poor Day 3 Embryos

Making it to Blastocyst

Good Day 3 Embryo 253/383

66%

Poor Day 3 Embryo 300/872

34%

P Value

Age of Eggs

Age of Eggs