Prospective Randomized Sibling-Oocyte Trial Comparing Fertilization and Embryo Development Outcomes Between Intracytoplasmic Sperm Injection (ICSI) and Conventional IVF Using Frozen Donor Sperm

This is a prospective, randomized sibling-oocyte controlled trial designed to compare fertilization and embryo development outcomes between intracytoplasmic sperm injection (ICSI) and conventional in vitro fertilization (IVF) using cryopreserved donor sperm in non-male factor infertility cycles. Despite widespread use of ICSI in assisted reproductive technology (ART), there is insufficient evidence supporting its routine use in non-male factor indications, especially in cycles utilizing frozen sperm where male factor infertility is not a contributing variable.

The study aims to address ongoing clinical debate and practice variation by evaluating whether ICSI offers meaningful advantages over conventional IVF in this specific context. Previous retrospective and meta-analytic data have suggested that while ICSI may reduce total fertilization failure (TFF), it may not improve-and may even negatively impact-other key clinical outcomes such as blastulation rate, embryo quality, and early pregnancy rates in non-male factor populations. Additionally, concerns about increased pregnancy-related complications with ICSI have been raised.

To reduce inter-patient variability and enhance internal validity, a sibling-oocyte design will be employed, allowing within-patient comparison of insemination methods. Oocytes retrieved from each participant will be randomized to either ICSI or conventional IVF. Randomization will be conducted prior to oocyte retrieval using computer-generated allocation. For patients with an even number of mature oocytes, half will be assigned to each insemination method. For those with an odd number, the extra oocyte will be randomly allocated according to the pre-specified scheme.

The fertilization process will begin shortly after oocyte retrieval. In the conventional IVF arm, mature oocytes will be inseminated using washed frozen-thawed donor sperm at a standard concentration and co-incubated for 16-18 hours. In the ICSI arm, a single motile sperm will be injected directly into each mature oocyte. All oocytes will undergo standard embryological assessment post-insemination, and embryos will be cultured under identical conditions.

The primary endpoint is the blastulation rate, defined as the number of usable blastocysts (meeting lab criteria for cryopreservation or transfer) per number of oocytes inseminated in each arm. Secondary outcomes include: