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Fresh versus frozen embryo transfers in assisted reproduction

Overview of attention for article published in Cochrane database of systematic reviews, March 2017
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Citations

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35 Dimensions

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Title
Fresh versus frozen embryo transfers in assisted reproduction
Published in
Cochrane database of systematic reviews, March 2017
DOI 10.1002/14651858.cd011184.pub2
Pubmed ID
Authors

Kai Mee Wong, Madelon van Wely, Femke Mol, Sjoerd Repping, Sebastiaan Mastenbroek

Abstract

In general, in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) implies a single fresh and one or more frozen-thawed embryo transfers. Alternatively, the 'freeze-all' strategy implies transfer of frozen-thawed embryos only, with no fresh embryo transfers. In practice, both strategies can vary technically including differences in freezing techniques and timing of transfer of cryopreservation, that is vitrification versus slow freezing, freezing of two pro-nucleate (2pn) versus cleavage-stage embryos versus blastocysts, and transfer of cleavage-stage embryos versus blastocysts.In the freeze-all strategy, embryo transfers are disengaged from ovarian stimulation in the initial treatment cycle. This could avoid a negative effect of ovarian hyperstimulation on the endometrium and thereby improve embryo implantation. It could also reduce the risk of ovarian hyperstimulation syndrome (OHSS) in the ovarian stimulation cycle by avoiding a pregnancy.We compared the benefits and risks of the two treatment strategies. To evaluate the effectiveness and safety of the freeze-all strategy compared to the conventional IVF/ICSI strategy in women undergoing assisted reproductive technology. We searched the Cochrane Gynaecology and Fertility Group Trials Register, the Cochrane Central Register of Studies (CRSO), MEDLINE, Embase, PsycINFO, CINAHL, and two registers of ongoing trials in November 2016 together with reference checking and contact with study authors and experts in the field to identify additional studies. We included randomised clinical trials comparing a freeze-all strategy with a conventional IVF/ICSI strategy which includes fresh transfer of embryos in women undergoing IVF or ICSI treatment. We used standard methodological procedures recommended by Cochrane. The primary review outcomes were cumulative live birth and OHSS. Secondary outcomes included other adverse effects (miscarriage rate). We included four randomised clinical trials analysing a total of 1892 women comparing a freeze-all strategy with a conventional IVF/ICSI strategy. The evidence was of moderate to low quality due to serious risk of bias and (for some outcomes) serious imprecision. Risk of bias was associated with unclear blinding of investigators for preliminary outcomes of the study, unit of analysis error, and absence of adequate study termination rules.There was no clear evidence of a difference in cumulative live birth rate between the freeze-all strategy and the conventional IVF/ICSI strategy (odds ratio (OR) 1.09, 95% confidence interval (CI) 0.91 to 1.31; 4 trials; 1892 women; I(2) = 0%; moderate-quality evidence). This suggests that if the cumulative live birth rate is 58% following a conventional IVF/ICSI strategy, the rate following a freeze-all strategy would be between 56% and 65%.The prevalence of OHSS was lower after the freeze-all strategy compared to the conventional IVF/ICSI strategy (OR 0.24, 95% CI 0.15 to 0.38; 2 trials; 1633 women; I(2) = 0%; low-quality evidence). This suggests that if the OHSS rate is 7% following a conventional IVF/ICSI strategy, the rate following a freeze-all strategy would be between 1% and 3%.The freeze-all strategy was associated with fewer miscarriages (OR 0.67, 95% CI 0.52 to 0.86; 4 trials; 1892 women; I(2) = 0%; low-quality evidence) and a higher rate of pregnancy complications (OR 1.44, 95% CI 1.08 to 1.92; 2 trials; 1633 women; low-quality evidence). There was no difference in multiple pregnancies per woman after the first transfer (OR 1.11, 95% CI 0.85 to 1.44; 2 trials; 1630 women; low-quality evidence), and no data were reported for time to pregnancy. We found moderate-quality evidence showing that one strategy is not superior to the other in terms of cumulative live birth rates. Time to pregnancy was not reported, but it can be assumed to be shorter using a conventional IVF/ICSI strategy in the case of similar cumulative live birth rates, as embryo transfer is delayed in a freeze-all strategy. Low-quality evidence suggests that not performing a fresh transfer lowers the OHSS risk for women at risk of OHSS.

Twitter Demographics

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Mendeley readers

The data shown below were compiled from readership statistics for 94 Mendeley readers of this research output. Click here to see the associated Mendeley record.

Geographical breakdown

Country Count As %
Unknown 94 100%

Demographic breakdown

Readers by professional status Count As %
Student > Master 21 22%
Unspecified 18 19%
Researcher 14 15%
Student > Doctoral Student 9 10%
Student > Bachelor 8 9%
Other 24 26%
Readers by discipline Count As %
Medicine and Dentistry 43 46%
Unspecified 22 23%
Nursing and Health Professions 10 11%
Biochemistry, Genetics and Molecular Biology 7 7%
Social Sciences 4 4%
Other 8 9%

Attention Score in Context

This research output has an Altmetric Attention Score of 4. This is our high-level measure of the quality and quantity of online attention that it has received. This Attention Score, as well as the ranking and number of research outputs shown below, was calculated when the research output was last mentioned on 08 June 2017.
All research outputs
#3,403,335
of 12,527,219 outputs
Outputs from Cochrane database of systematic reviews
#6,176
of 9,882 outputs
Outputs of similar age
#86,298
of 256,094 outputs
Outputs of similar age from Cochrane database of systematic reviews
#147
of 216 outputs
Altmetric has tracked 12,527,219 research outputs across all sources so far. This one has received more attention than most of these and is in the 72nd percentile.
So far Altmetric has tracked 9,882 research outputs from this source. They typically receive a lot more attention than average, with a mean Attention Score of 20.5. This one is in the 36th percentile – i.e., 36% of its peers scored the same or lower than it.
Older research outputs will score higher simply because they've had more time to accumulate mentions. To account for age we can compare this Altmetric Attention Score to the 256,094 tracked outputs that were published within six weeks on either side of this one in any source. This one has gotten more attention than average, scoring higher than 65% of its contemporaries.
We're also able to compare this research output to 216 others from the same source and published within six weeks on either side of this one. This one is in the 31st percentile – i.e., 31% of its contemporaries scored the same or lower than it.