The VILOCITY Trial: Validating Incubators in the Lab, Optimizing Culture and Investigating BlasTulation Yield, a...

To determine whether the use of a benchtop incubator for embryo culture improves blastulation rates compared with a conventional box incubator.

Prospective split cohort double-blind RCT at a single academic-affiliated center.

Patients undergoing IVF with PGT-A and planning a subsequent frozen single euploid embryo transfer were recruited between December 2023 and January 2025.

The primary exposure was culture in a benchtop incubator. Patients with ≥4 metaphase II (MII) oocytes at the time of vaginal oocyte retrieval were randomized. Retrieved MII oocytes were allocated by block randomization in a 1:1 ratio, with half cultured in the benchtop incubator and half in a conventional box incubator. All other embryology procedures, media and developmental checkpoints were standardized between groups.

The primary outcome was blastulation rate per MII oocyte. Secondary outcomes included fertilization rate, blastulation rate per 2-pronuclear (2PN) embryo, embryo grade and morphology, and ploidy rates. Clinical outcomes following subsequent frozen euploid embryo transfer were also assessed, including ongoing pregnancy rate (OPR), pregnancy loss, and live birth rate (LBR).

A total of 2,152 MII oocytes from 145 patients were randomized and included in the primary analysis. Blastulation rate per MII was identical between box and benchtop incubators (51% vs 51%, p=0.73). Fertilization rate (84% vs 86%, p=0.31), blastulation rate per 2PN (61% vs 59%, p=0.68), and euploid rate (69% vs 66%, p=0.43) were also comparable between groups. Embryo grading did not differ by incubator, including day of blastulation (p=0.46), expansion grade (p=0.16), inner cell mass grade (p=0.33), or trophectoderm grade (p=0.97). Among 133 frozen embryo transfers (69 box, 64 benchtop), pregnancy outcomes were comparable between groups. Ongoing pregnancy rate was 67% in the box group versus 64% in the benchtop group (p=0.90). Pregnancy loss (biochemical and clinical) occurred in 9% versus 20% (p=0.10), and live birth rate was 67% versus 61% (p=0.74), respectively.

In this RCT, culture in a benchtop incubator did not improve blastulation rate per MII compared with a conventional box incubator. Other embryologic and pregnancy outcomes were also comparable between incubator types, indicating that when other variables are controlled, the incubator alone does not meaningfully influence outcomes.