| Study |
Bias |
| Randomisation process |
Deviations from intended interventions |
Missing outcome data |
Measurement of the outcome |
Selection of the reported results |
Overall |
| Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
Authors' judgement |
Support for judgement |
| Subgroup 4.2.1 equal number of embryos transferred |
| Aziminekoo 2015 |
Some concerns |
No information about the allocation sequence concealed but no baseline differences between groups. |
Some concerns |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols. All randomised women were analysed. |
Low risk of bias |
All 118 randomised women were available. |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to randomisation process, deviations from the intended interventions and selection of reported results. |
| Bungum 2003 |
Low risk of bias |
There was not a complete explanation about concealment and there are some concerns about baseline differences |
Low risk of bias |
No effort for blindness is described. Considering the nature of the intervention, it is very unlikely that participants and carers and people delivering the intervention were not aware of their assigned intervention. |
Low risk of bias |
All 118 randomised women were analysed. |
Low risk of bias |
Method of measuring the outcome was probably appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
Some concerns of risk of bias due to selection of reported results |
| Coskun 2000 |
Low risk of bias |
Randomisation process apparently has no problems. Patients were randomized to receive embryo transfer either at day 3 or day 5. Quote " An equal number of ‘day 3' or ‘day 5' labels placed in sealed envelopes in a block of 14 was kept in a box and an envelope was drawn by the embryologist as soon as a patient qualified for the study. The label was attached with adhesive to the patients’ data collection sheet." |
Some concerns |
Participants and carers and people delivering the intervention were probably aware of their assigned intervention. |
Low risk of bias |
All 201 randomised women were available. |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
Some concerns due to deviation from intended interventions and selection of reported outcomes |
| Fernandez‐Shaw 2015 |
Some concerns |
No statement about allocation concealment. |
Low risk of bias |
No effort for blindness is described. Considering the nature of the intervention, it is very unlikely that participants and carers and people delivering the intervention were not aware of their assigned intervention. |
Low risk of bias |
All women randomised were analysed |
Low risk of bias |
Method of measuring the outcome was probably appropriate, in both groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There some concerns of risk of bias due to the randomisation process and selection of reported results. |
| Hatirnaz 2017 |
Some concerns |
No information about the allocation sequence concealed but no baseline differences between groups. |
Some concerns |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols. Analysis was performed by intention‐to‐treat. |
Low risk of bias |
95 out of 100 women of each arm had data to analyze |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to randomisation process, deviations from the intended interventions and selection of reported results. |
| Hreinsson 2004 |
Low risk of bias |
Allocation sequence was random and concealed. Quote:"Sealed envelopes were used for randomisation of the patients for each group". Groups were balanced. |
Low risk of bias |
No effort for blindness is described. Considering the nature of the intervention, it is very unlikely that participants and carers and people delivering the intervention were not aware of their assigned intervention. No differences in embryos per transfer bat there was for cycles with embryo freezing. All women randomised were analyses by assignement |
Low risk of bias |
All women randomised were analysed |
Low risk of bias |
Knowledge of the assigned intervention is unlikely to influence this objective outcome assessment. |
Some concerns |
No protocol registration was found. |
Some concerns |
Some concerns of risk of bias due to selection of reported results. |
| Kaur 2014 |
Some concerns |
No information if the allocation sequence was random and/or concealed but no baseline differences between groups. |
Some concerns |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols. Analysis was performed by intention‐to‐treat. |
Low risk of bias |
All the randomized women were analysed. |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to randomisation process, deviations from the intended interventions and selection of reported results. |
| Kolibianakis 2004 |
High risk of bias |
Allocation sequence was random but it was not concealed. No baseline differences between groups were found. |
High risk of bias |
Participants, carers and people delivering the intervention were aware of their assigned intervention. No information about a deviation from the intended protocols. No information if there was a substantial impact of the failure to analyse participants in the group to which they were randomized. |
Low risk of bias |
All randomised women were analysed |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
High risk of bias |
There are high of risk of bias due to deviations from the intended interventions and randomisation process, and some concerns of risk of bias due to selection of reported results. |
| Levi‐Setti 2018 |
Some concerns |
Allocation sequence was not concealed but no baseline clinical and statistical differences between groups were found in a table that described more than 15 different variables. |
Low risk of bias |
Participants and embryologists were aware of their assigned intervention. No deviation from the intended protocols. Analysis was performed by intention‐to‐treat. |
Low risk of bias |
No lost to follow up |
Low risk of bias |
Method of measuring the outcome was not informed. However, given the nature of the outcome and the methods to measure it, it was probably not different between groups and, as it is an objective outcome, it is unlikely to be influenced by the knowledge of the assigned intervention. |
Low risk of bias |
Data that produced this result was analysed in accordance with a pre‐specified analysis plan that was finalized before unblinded outcome data were available for analysis |
Some concerns |
There is some concerns of risk of bias due to randomisation process. |
| Papanikolaou 2005 |
Some concerns |
No information about the allocation sequence concealed but no baseline differences between groups. |
Some concerns |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols. All randomised women were analysed. |
Low risk of bias |
All the randomized women were analysed. |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to randomisation process, deviations from the intended interventions and selection of reported results. |
| Papanikolaou 2006 |
Some concerns |
There was not enough information to evaluate the method of allocation sequence concealment. |
Low risk of bias |
Participants were probably aware of their assigned intervention. No deviation from the intended protocols. All randomised women were analysed. |
Low risk of bias |
All the randomized women were analysed |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to randomisation process and selection of reported results. |
| Rienzi 2002 |
Some concerns |
No information about the allocation sequence concealed but no baseline differences between groups. |
High risk of bias |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols and no information about the total number of randomised women. |
High risk of bias |
No information about neither the total number of randomized women nor the missing outcome data. |
Low risk of bias |
Method of measuring the outcome was appropriate, it was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
High risk of bias |
There is high risk of bias due to deviations from the intended interventions, and there are some concerns of risk of bias due to randomisation process, missing outcomes and selection of reported results. |
| Van der Auwera 2002 |
Low risk of bias |
No information available to know if the allocation sequence was random. However, allocation sequence was concealed and no baseline differences between groups. |
Some concerns |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. There were only few with deviation from the intended protocols, and no imbalance was found. All randomised women were analysed. |
Low risk of bias |
Quote: “Three patients were excluded for analysis from group 1 because they wanted an elective blastocyst culture while four patients were excluded from group 2 because they wanted an elective day 2 transfer.” |
Low risk of bias |
Method of measuring the outcome was not described. However, it is unlikely that it was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to deviations from the intended interventions and selection of reported results. |
| Yang 2018 |
Low risk of bias |
Allocation sequence was random and concealed |
Some concerns |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols. And no information about the number of randomised women per arm and it is not possible to know how the analysis was performed. |
Low risk of bias |
The observed number of events is much greater than the number of participants with missing outcome data, but it is probably not related with the true value |
Low risk of bias |
Method of measuring the outcome was appropriate, it was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Low risk of bias |
Quote" ChiCTR‐ICR‐15006600" |
Some concerns |
There are some concerns of risk of bias due to deviations from the intended interventions. |
| Subgroup 4.2.2 more cleavage stage than blastocyst embryos transferred |
| Elgindy 2011 |
Some concerns |
The number of embryos per transfer was significantly higher in group than the other group |
Some concerns |
This open‐label, prospective, randomized, controlled trial. No information about a deviation from the intended protocols |
Low risk of bias |
All ranomised women were analysed |
Low risk of bias |
Knowledge of the assigned intervention is unlikely to influence this objective outcome assessment. |
Some concerns |
No protocol registration was found. |
Some concerns |
There some concerns of risk of bias due to the randomisation process, deviations from intended interventions and selection of reported results. |
| Emiliani 2003 |
Some concerns |
Concealment was not stated. Only minor differences in age |
Low risk of bias |
No effort for blindness is described. Considering the nature of the intervention, it is very unlikely that participants and carers and people delivering the intervention were not aware of their assigned intervention. |
Low risk of bias |
All women randomised were analysed |
Low risk of bias |
Not reported but inappropriate methotds are unlikely. It is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention |
Some concerns |
No protocol registration was found. |
Some concerns |
There some concerns of risk of bias due to the randomisation process and selection of reported results. |
| Frattarelli 2003 |
Low risk of bias |
Randomization was accomplished using a computer‐generated randomization table. The sequences of randomization were concealed until intervention was assigned. The groups were balanced. Concealment method was not described. |
High risk of bias |
Those patients undergoing a day 5 ET had a significantly higher implantation rate than those undergoing a day 3, these deviations likely have affected the outcome |
Low risk of bias |
All women randomised were analysed |
Low risk of bias |
Method of measuring the outcome was probably appropriate, no different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
High risk of bias |
High risk of bias due to deviations from the intended protocol and some concerns due to bias in selection of the reported result. |
| Karaki 2002 |
Low risk of bias |
No information if the allocation sequence was random, but it was concealed and no baseline differences were found between groups. |
High risk of bias |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. There was probably a deviation from the intended protocols. All randomised women were analysed. |
Low risk of bias |
No missing outcome data. |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
High risk of bias |
There is high risk of bias due to deviations of the protocol and some concerns of risk of bias due to selection of reported results. |
| Levitas 2004 |
Low risk of bias |
Allocation sequence was random and concealed and no baseline differences were found between groups. |
High risk of bias |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. There was probably a deviation from the intended protocols. Analysis was done by ITT |
Low risk of bias |
Although there are missing outcome data, the missingness in the outcome probably does not depend on its true value. |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
High risk of bias |
There is high risk of bias due to devitations of the protocol and some concerns of risk of bias due to selection of reported results. |
| Levron 2002 |
Some concerns |
No information if the allocation sequence was random and concealed but no baseline differences between groups. |
Low risk of bias |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols. Analysis was performed by intention‐to‐treat. |
Low risk of bias |
Only 3 out of 46 in the blastocyst group did not have embryo transfer |
Low risk of bias |
Method of measuring the outcome was not stated, but it is not probable that it was measured different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to randomisation process and selection of reported results. |
| Livingstone 2002 |
Low risk of bias |
Allocation sequence was random and concealed |
High risk of bias |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. There was evidencesuggesting deviation from the intended protocols. All randomised women were analysed. |
Low risk of bias |
All the randomized women were analysed |
Low risk of bias |
Method of measuring the outcome was not described. However, it is unlikely that it was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
High risk of bias |
There is high risk of bias due to deviations from the intended interventions and there are some concerns of risk of bias due to the selection of reported results. |
| Motta 1998 |
Some concerns |
No information available to know if the allocation sequence was random or the allocation sequence was concealed. And no information about baseline differences between groups. |
High risk of bias |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. There was evidencesuggesting deviation from the intended protocols. All randomised women were analysed. |
Low risk of bias |
No lost to follow up |
Low risk of bias |
Method of measuring the outcome was not described. However, it is unlikely that it was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
High risk of bias |
There is high risk of bias due to deviations from the intended interventions and there are some concerns of risk of bias due to the randomisation process and selection of reported results. |
| Subgroup 4.2.3 single embryo transfer |
| Papanikolaou 2006 |
Some concerns |
There was not enough information to evaluate the method of allocation sequence concealment. |
Low risk of bias |
Participants were probably aware of their assigned intervention. No deviation from the intended protocols. All randomised women were analysed. |
Low risk of bias |
All the randomized women were analysed |
Low risk of bias |
Method of measuring the outcome was appropriate, was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Some concerns |
No protocol registration was found. |
Some concerns |
There are some concerns of risk of bias due to randomisation process and selection of reported results. |
| Yang 2018 |
Low risk of bias |
Allocation sequence was random and concealed |
Some concerns |
Participants, carers and people delivering the intervention were probably aware of their assigned intervention. No information about a deviation from the intended protocols. And no information about the number of randomised women per arm and it is not possible to know how the analysis was performed. |
Low risk of bias |
The observed number of events is much greater than the number of participants with missing outcome data, but it is probably not related with the true value |
Low risk of bias |
Method of measuring the outcome was appropriate, it was not different between groups and it is an objective outcome that is unlikely to be influenced by the knowledge of the assigned intervention. |
Low risk of bias |
Quote" ChiCTR‐ICR‐15006600" |
Some concerns |
There are some concerns of risk of bias due to deviations from the intended interventions. |
