Abstract:
Background Embryo quality is a determinant factor affecting reproductive and birth outcomes. Oocyte maturation is usually assessed indirectly using the diameters of follicles measured by ultrasound. However, ultrasound measurement is difficult and has low accuracy in the condition of multiple follicles development. More accurate data are needed to support the widely used empirical value and trigger time in clinical practice.
Objective To explore the relationship between follicle size and fertilization and embryo quality using more accurate indexes by directly measuring follicular fluid volume and average diameter.
Methods From September 2022 to January 2023, a total of 42 infertile couples who received assisted reproductive technology at the Reproductive Center of the First Medical Center of Chinese PLA General Hospital participated in the study. Each follicle was individually punctured and removed under ultrasound, and the follicular fluid volume was measured. Follicle diameter was calculated by measuring the volume formula V=4/3πR3. The follicles were divided into 7 groups according to the converted diameter: <13mm, 13-15 mm, 15-17 mm, 17-19 mm, 19-21 mm, 21-23 mm, ≥23 mm. The oocytes, zygotes and embryos corresponding to each follicle were operated separately, and the development of the embryos was observed.
Results The mean age of 42 assisted reproductive women was 36.27 ± 4.34 years old. A total of 277 oocytes were collected, 122 zygotes were formed, and 122 embryos were obtained (including 97 high-quality embryos). Follicles < 13 mm had the highest fertility rate of oocyte (83.3%). However, there was no significant difference between follicle size and fertility rate (P>0.05). There were statistical differences in the rate of excellent embryos among follicles of different sizes (P<0.05). Excellent embryo rate of follicles with the diameter of 13-15mm was the highest (87.5%). The excellent embryo rate of follicles with the diameter of 13-21 mm was significantly higher than other larger follicles (P=0.017), and follicles with the diameter of 17-19 mm were the best (P=0.033).
Conclusion Follicle size is significantly correlated to the quality of zygote and embryo. Smaller follicles are difficult to form high-quality embryos, but oversized follicles will also reduce embryo quality. The embryos obtained from follicles with the diameter of 17-19 mm have higher quality and better viability.