Clinical parameters influencing human zona pellucida thickness

Area of Science:

• Reproductive biology
• In vitro fertilization (IVF)
• Oocyte maturation

Background:

• Zona pellucida (ZP) thickness is a critical factor in human oocyte fertilization.
• Understanding factors influencing ZP thickness is essential for optimizing IVF outcomes.
• Previous research has explored various parameters, but a comprehensive analysis linking clinical factors to ZP thickness is needed.

Purpose of the Study:

• To determine which clinical parameters significantly influence human oocyte zona pellucida (ZP) thickness.
• To investigate the relationship between ZP thickness and fertilization rates in IVF cycles.

Main Methods:

• Measurement of ZP thickness in 827 oocytes from 75 IVF-ET cycles using an inverted light microscope.
• Analysis of clinical parameters including female age, stimulation duration, oocyte maturity, retrieved oocytes, hMG dosage, E2 levels, and follicular volume.
• Regression analysis to identify significant correlations between ZP thickness and clinical parameters.

Main Results:

• Mean ZP thickness varied significantly between unfertilized (18.9 ± 3.8 μm), fertilized (16.4 ± 3.1 μm), and polyspermic (15.1 ± 2.4 μm) oocytes.
• A significant inverse linear relationship was observed between ZP thickness and maximum estradiol (E2) levels.
• A significant positive linear relationship was found between ZP thickness and the total dose of human menopausal gonadotropin (hMG).

Conclusions:

• Human oocyte ZP thickness is primarily an individual characteristic that impacts fertilization rates.
• Hormonal stimulation protocols, specifically maximum E2 levels and hMG dosage, can exert a slight influence on ZP thickness.