Manual screening of follicular fluid during in vitro fertilization may miss additional oocytes, including mature oocytes capable of fertilization and blastocyst development, according to a multicenter clinical study published in Nature Medicine.

Using an automated microfluidic device, researchers recovered additional oocytes from samples that had already been screened and discarded under standard clinical practice. Some of these oocytes developed into high-quality embryos, and in one case, resulted in a live birth.

The study evaluated a microfluidic isolation and denudation system known as FIND-Chip, designed to automate oocyte recovery from follicular fluid. In a clinical investigation involving 582 patients across four in vitro fertilization (IVF) centers, the device was applied to follicular fluid that embryologists had deemed fully screened. Researchers recovered at least one additional oocyte in more than half of cases.

Across all processed samples, the system recovered 583 additional oocytes, of which just over 40% were mature metaphase II oocytes suitable for immediate clinical use. In a pilot clinical return cohort, these recovered oocytes demonstrated fertilization and blastocyst development rates similar to those observed with manually recovered oocytes. Because of the small sample size, these findings were descriptive and not statistically compared, but no signal of reduced developmental potential was observed.

In the pilot return study, extra oocytes recovered by FIND-Chip were reintegrated into patient treatment cycles. Among 19 patients, 11 gained at least one additional oocyte, expanding the available embryo pool. Two patients obtained additional blastocysts for cryopreservation, and one achieved a live birth from an oocyte that would otherwise have been discarded following routine screening.

Researchers note that manual follicular fluid screening has remained largely unchanged for decades and relies on visual identification by trained embryologists — a process complicated by blood cells, tissue debris, and variability in sample composition. By contrast, the microfluidic system isolates oocytes based on size and physical properties rather than visual recognition, enabling recovery of oocytes that may be difficult to detect under a microscope.

Beyond individual cases, the findings raise broader questions about IVF laboratory efficiency. Oocyte yield is associated with cumulative live birth rates, particularly among patients with diminished ovarian reserve, and recovering additional viable oocytes could potentially influence treatment outcomes. Larger studies would be needed to quantify any impact on cumulative live birth rates.

Researchers suggest that automated screening technologies may help standardize laboratory processes across clinics, reduce reliance on highly specialized manual labor, and improve efficiency in IVF workflows.

Disclosures can be found in the study.

Source: Nature Medicine