SISTER: Sibling Oocyte Insemination With Frozen Sperm From Third Party Donors: Evaluation of Reproductive Techniques

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:

• Fertilization rate: number of 2PN zygotes per oocyte inseminated
• Incidence of TFF: no oocytes fertilized in a given arm
• Proportion of high-quality blastocysts, defined as grade BB or higher
• Early clinical pregnancy rate, as determined by ultrasound-confirmed intrauterine gestation Statistical analysis will use generalized estimating equations (GEE) for the primary outcome at the oocyte level to account for clustering within patients. Secondary outcomes will be analyzed using chi-square or Fisher's exact tests as appropriate. All data will be analyzed on an intention-to-treat basis.

The study will enroll approximately 178 participants over 12 months at Shady Grove Fertility, where frozen donor sperm with normal post-thaw parameters is routinely available. Only non-male factor infertility patients using frozen donor sperm will be eligible, ensuring a controlled sperm quality baseline across study arms.

The hypothesis is that conventional IVF will demonstrate equivalent or superior blastulation rates compared to ICSI, with non-inferior fertilization outcomes and potentially better embryo morphology. Results from this trial will help refine clinical guidelines and may support a more evidence-based, resource-efficient use of ICSI.

IRB approval has been obtained, and informed consent will be secured from all participants. All procedures will adhere to Good Clinical Practice and applicable regulatory guidelines. Data confidentiality will be maintained throughout.

Inclusion criteria

• Female patients undergoing IVF with frozen donor sperm at Shady Grove Fertility Center
• Normal ovarian reserve (AMH > 1 ng/mL, AFC > 10)
• Absence of male factor infertility
• Post-wash parameters: >50% motility, >5mil concentration
• > 4 oocytes retrieved at time of transvaginal oocyte retrieval

Exclusion criteria

• Donor Sperm with significant male factor infertility (e.g., abnormal sperm concentration, motility, or morphology)
• Any medical condition contraindicating ART