Various interventions have been proposed to improve embryo implantation in IVF. Among these, intrauterine injections of human chorionic gonadotropin seem to have promising results. Consequently, we conducted a review and meta-analysis to assess IVF outcomes by comparing couples who underwent intrauterine hCG injection transfer versus those who underwent embryo transfer with intrauterine injection of placebo, or without any additional intervention. The primary outcome was the clinical pregnancy rate. Secondary outcomes were the implantation rate, miscarriage rate, and live birth rate. A meta-analysis was conducted using the random effects model, while bias within studies was detected using the Cochrane risk of bias tool. Ectopic pregnancies and stillbirths were also assessed. The clinical pregnancy (RR 1.38, 95% CI 1.17−1.62, p < 0.0001) and implantation rate (RR 1.40, 95% CI 1.12−1.75, p = 0.003) were significantly higher in women who underwent hCG injection than in the control group. These significant effects persisted only in women who underwent cleavage-stage embryo transfer. No significant differences between groups were observed in the other secondary outcomes. In conclusion, our systematic review and meta-analysis demonstrate that intrauterine injection of hCG could be a valuable approach in women who undergo cleavage-stage embryo transfer. Given the lack of data about the live birth rate, caution should be exercised in interpreting these data.
Keywords: ART; ICSI; IVF; embryo implantation; hCG; intrauterine administration.