Summary of findings 2. Fresh compared to frozen embryo transfers in assisted reproduction regarding pregnancy and neonatal outcomes.
| Fresh compared to frozen embryo transfers in assisted reproduction regarding pregnancy and neonatal outcomes (cumulatively and after first embryo transfer) | ||||||
| Patient or population: women undergoing assisted reproduction Setting: assisted reproduction clinic Intervention: frozen embryo transfers only Comparison: fresh and frozen embryo transfers (conventional IVF) | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | № of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Risk with fresh and frozen embryo transfers | Risk with frozen embryo transfer only | |||||
| Hypertensive disorders of pregnancy: cumulatively | 26 per 1000 | 18 per 1000 (7 to 46) | OR 0.70 (0.27 to 1.82) | 782 (1 RCT) | ⊕⊕⊝⊝ Lowa,b | |
| Hypertensive disorders of pregnancy: after first ET | 15 per 1000 | 31 per 1000 (21 to 46) | OR 2.15 (1.42 to 3.25) | 3940 (3 RCTs) | ⊕⊕⊝⊝ Lowa,b | |
| Large for gestational age (birth weight above 90th percentile): cumulatively | 10 per 1000 | 20 per 1000 (6 to 60) | OR 1.97 (0.63 to 6.15) | 782 (1 RCT) | ⊕⊕⊝⊝ Lowa,b | |
| Large for gestational age (birth weight above 90th percentile): after first ET | 42 per 1000 | 79 per 1000 (62 to 100) | OR 1.96 (1.51 to 2.55) | 3940 (3 RCTs) | ⊕⊕⊝⊝ Lowa,b,c | |
| Small for gestational age (birth weight below 10th percentile): cumulatively | 46 per 1000 | 17 per 1000 (8 to 37) | OR 0.36 (0.16 to 0.80) | 782 (1 RCT) | ⊕⊕⊝⊝ Lowa,b | |
| Small for gestational age (birth weight below 10th percentile): after first ET | 82 per 1000 | 68 per 1000 (55 to 86) | OR 0.82 (0.65 to 1.05) | 3940 (3 RCTs) | ⊕⊝⊝⊝ Very lowa,b,c | |
| Birth weight of babies born: singletons | MD 127.4 g higher (77.1 higher to 177.1 higher) | ‐ | 1607 (5 RCTs) | ⊕⊕⊕⊝ Moderatea | ||
| Birth weight of babies born: multiples | MD 49.5 g higher (21.1 lower to 120.1 higher) | ‐ | 804 (4 RCTs) | ⊕⊕⊝⊝ Lowa,c | ||
| *The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: confidence interval; IVF: in vitro fertilisation; MD: mean difference; OR: odds ratio; RCT: randomised controlled trial; RR: risk ratio | ||||||
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GRADE Working Group grades of evidence High quality: further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: we are very uncertain about the estimate. | ||||||
aDowngraded one level due to serious risk of bias associated with lack of power calculation (unclear what determined end of study) and/or use of interim analysis that was calculated per transfer (unit of analysis error) with absence of adequate stopping rules (possible overestimation of treatment effect). bDowngraded one level due to serious imprecision: event rate: less than 300. cDowngraded one level due to serious unexplained heterogeneity.