Time of insemination culture and outcomes of in vitro fertilization: a systematic review and meta-analysis

BACKGROUND Conflicting results have been reported regarding the technique of brief insemination used in IVF. The aim of this meta-analysis was to determine if better clinical outcomes of IVF are associated with a brief co-incubation of gametes than with a standard overnight co-incubation. METHODS A computerized search was conducted of the published literature of four databases, using search terms related to gamete, time of co-incubation and outcome measure. Eligible studies compared outcomes of IVF with a brief co-incubation of gametes to that of a control group of standard insemination and reported rates of live birth (primary outcome), normal fertilization, polyspermy, good quality embryos, implantation, clinical pregnancy or ongoing pregnancy (secondary outcomes). A total of 11 studies were included in the meta-analysis. Pooled risk ratios (RRs) and 95% confidence intervals (CIs) were calculated for the data. Statistical heterogeneity was tested using Cochran Q and I² values. RESULTS Brief co-incubation of gametes was associated with significantly higher rates of clinical pregnancy (RR: 1.84, 95% CI: 1.24-2.73) and ongoing pregnancy (RR: 1.73, 95% CI: 1.27-2.33) than standard insemination. Brief co-incubation of gametes was associated also with a significantly higher rate of implantation (RR: 1.80, 95% CI: 1.43-2.26) than standard insemination. However, the rates of normal fertilization (RR: 0.98, 95% CI: 0.93-1.02), good quality embryos (RR: 1.24, 95% CI: 1.0-1.53) and polyspermy (RR: 0.84, 95% CI: 0.7-1.01) were not significantly different with brief co-incubation of gametes compared with standard insemination. CONCLUSIONS Reduced gamete exposure time may be associated with beneficial outcomes. Drawbacks inherent to the quality of several studies limit the quality of the available evidence. Adequately powered randomized controlled studies need to be performed to evaluate the efficacy of brief insemination.