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Individual participant data meta-analysis of randomised controlled trials comparing elective freezing of embryos followed by thawed frozen embryo transfer versus fresh embryo transfer in in-vitro fertilisation

Project Description

Background to the project
During in-vitro fertilisation (IVF), women are treated with hormone injections so that their ovaries can produce multiple eggs. These eggs are collected and mixed with sperm to produce embryos. The embryos develop for a few days in the laboratory and the best quality embryo(s) is selected and put into the womb (a procedure called a fresh embryo transfer). Spare embryos are frozen for replacement later (frozen embryo transfer). However, it is thought that delaying the first embryo transfer allows the effect of the hormonal treatment to wear off such that the uterus is more receptive to the replaced embryo, thus increasing the chances of pregnancy. Research has also shown that frozen embryo transfer could be safer for the mother and the baby as it is less likely to cause low birthweight and prematurity. Some clinics are already shifting to a strategy of freezing all suitable embryos and transferring them at a later date, but it is not clear whether this genuinely increases the success or safety of IVF. This strategy may only be better for certain groups of women. Many worldwide randomised controlled trials (RCTs) have compared pregnancy rates after fresh versus frozen embryo transfer. Although they have collected data on other outcomes such as complications in the mother and baby, the number of cases in each trial is too small to provide meaningful answers. This project will aim to collect and combine data from all trials to identify groups of women who may benefit most from fresh or frozen embryo transfer depending on their characteristics.

Proposed research and techniques
At least eleven of the RCTs (>7000 combined participants) will be included in this individual participant data meta-analysis (IPD-MA). The investigators of all these trials have pledged their support for a collaborative group and a well-developed protocol has been agreed. A systematic review of the literature will be conducted to search for other eligible trials not already identified.

This IPD-MA study will involve combining all RCTs into one large database. This will provide enough statistical power to detect any particular groups of women for whom transferring a frozen embryo has a better outcome than transferring a fresh embryo. Such analysis will adjust for the heterogeneity between trials.

You will join a collaborative team in the University of Aberdeen who are known in the world of fertility research for their expertise in observational and RCT studies. There will be opportunities to develop collaborations with researchers and clinicians from the various RCT centres. You will liaise with patient representatives to conduct this synthesis of global data to guide future national and international policy on IVF treatment. Patient representatives and the public have been integral in the design and conduct for the primary trials and will continue to support this project. As this is of both national and international importance, the results will be disseminated by individualized dissemination strategies for every group of stakeholders (patients, policy-makers, funders, clinicians and academics) across the globe.

Useful previous experience for the studentship
This project requires a numerically highly skilled student, preferably with a medical statistics qualification, who is interested in the meta-analysis of individual participant data and is motivated to perform high-quality research which will inform IVF policy worldwide. The University has an information page for prospective students here:
This project is advertised in relation to the research areas of APPLIED HEALTH SCIENCE. Formal applications can be completed online: You should apply for Degree of Doctor of Philosophy in Applied Health Science, to ensure that your application is passed to the correct person for processing.


Candidates should contact the lead supervisor to discuss the project in advance of submitting an application, as supervisors will be expected to provide a letter of support for suitable applicants. Candidates will be informed after the application deadline if they have been shortlisted for interview.

Funding Notes

This project is part of a competition funded by the Institute of Applied Health Sciences. Full funding is available to UK/EU candidates only. Overseas candidates can apply for this studentship but will have to find additional funding to cover the difference between overseas and home fees (approximately £15,680 per annum).

Candidates should have (or expect to achieve) a minimum of a First Class Honours degree in a relevant subject. Applicants with a minimum of a 2:1 Honours degree may be considered provided they have a Distinction at Masters level.

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