Round spermatid injection into human oocytes: a systematic review and meta-analysis

Many azoospermic men do not possess mature spermatozoa at the time of surgical sperm extraction. This study is a systematic review and meta-analysis evaluating outcomes following round spermatid injection (ROSI), a technique which utilizes immature precursors of spermatozoa for fertilization. An electronic search was performed to identify relevant articles published through October 2018. Human cohort studies in English involving male patients who had round spermatids identified and used for fertilization with human oocytes were included. Fertilization rate, pregnancy rate, and resultant delivery rate were assessed following ROSI. Meta-analysis outcomes were analyzed using a random-effects model. Data were extracted from 22 studies involving 1099 couples and 4218 embryo transfers. The fertilization rate after ROSI was 38.7% (95% confidence interval [CI]: 31.5%-46.3%), while the pregnancy rate was 3.7% (95% CI: 3.2%-4.4%). The resultant delivery rate was low, with 4.3% of embryo transfers resulting in a delivery (95% CI: 2.3%-7.7%). The pregnancy rate per couple was 13.4% (95% CI: 6.8%-19.1%) and the resultant delivery rate per couple was 8.1% (95% CI: 6.1%-14.4%). ROSI has resulted in clinical pregnancies and live births, but success rates are considerably lower than those achieved with mature spermatozoa. While this technique may be a feasible alternative for men with azoospermia who decline other options, couples should be aware that the odds of a successful delivery are greatly diminished and the prognosis is relatively poor.