# Optimization of Aspiration Pressure in Oocyte Retrieval Using Reduced Needles

## TL;DR

This study finds that lower aspiration pressure improves fertilization rates when using reduced needles in oocyte retrieval.

## Contribution

The study identifies optimal aspiration pressure for reduced needles based on shaft diameter rather than tip diameter.

## Key findings

- Lower aspiration pressure (160 mmHg) resulted in shorter procedure times for patients with AMH ≥1.2.
- Fertilization rates were significantly higher at 160 mmHg for both AMH ≥1.2 and AMH <1.2 groups.
- Aspiration pressure adjustments based on shaft diameter may improve outcomes in oocyte retrieval.

## Abstract

Introduction: In recent years, reduced needles have been developed with a thin tip and thick shaft, offering reduced pain compared to conventional thick needles without compromising clinical outcomes, leading to increased utilization. However, there has been no investigation of optimal aspiration pressure for reduced needles. Generally, aspiration pressure needs to be increased when the needle diameter is reduced. In this study, we investigated the optimal pressure for reduced needles with two different diameters.

Methods: We conducted a retrospective analysis of 223 cycles of oocyte retrieval performed at our facility from January 2023 to June 2025. Reduced needles with a 20-gauge tip and 17-gauge shaft were used, comparing aspiration pressures of 230 mmHg and 160 mmHg. We compared age, anti-Müllerian hormone (AMH) levels, procedure time, number of punctured follicles, number of retrieved oocytes, and number of fertilized oocytes between the two pressure groups.

Results: No significant differences were observed between the two groups in age, AMH levels, number of punctured follicles, number of retrieved oocytes, or number of fertilized oocytes. However, procedure time was significantly shorter in the 160 mmHg group when AMH ≥1.2 (p=0.009). While no significant difference was found in oocyte retrieval rates, fertilization rates were significantly higher in the 160 mmHg group for both AMH ≥1.2 and AMH <1.2 cases (p=0.009, 0.001, respectively).

Conclusions: In reduced needles, high aspiration pressure was associated with decreased fertilization rates in our study. Our findings suggest that adjusting aspiration pressure according to the thick shaft diameter rather than the thin tip diameter may be preferable.