Ultrastructural characteristics of the luteal phase endometrium in patients undergoing controlled ovarian hyperstimulation

Abstract

Objective: To provide a descriptive analysis of the ultrastructure of the endometrial surface epithelium during the luteal phase from patients undergoing controlled ovarian hyperstimulation (COH).

Design: Prospective, observational study.

Setting: Tertiary care academic IVF center.

Patient(s): Twelve oocyte donors undergoing COH.

Intervention(s): After oocyte aspiration, patients underwent two endometrial biopsies 2 to 7 days after hCG administration.

Main outcome measure(s): Appearance of the endometrial epithelial surface as evaluated by scanning electron microscopy.

Result(s): Endometrial maturation proceeded in an orderly manner. The ciliated cells remained unchanged, both in regards to cell density, cilia density, and ratio of ciliated cells to nonciliated cells. The microvilli became more uniformly distributed as the luteal phase progressed. The central aspect of the cells also appeared to protrude more into the endometrial lumen as the cycle progressed. Elongation the glandular orifices also was noted with progression of the luteal phase. Apical protrusions, pinopods, were noted to develop and regress during a short period during the midluteal phase spanning days 4 to 7 after hCG administration. Initial pinopod development began in the region of the glandular orifices, with substantially fewer occurring outside this region.

Conclusion(s): Although the development of the endometrial ultrastructural characteristics during the luteal phase progresses in an orderly manner that is comparable to that of endometrium obtained in unstimulated cycles, pinopod expression was noted at an earlier phase of endometrial maturation. This advanced development may result in an alteration the window of implantation and affect pregnancy rates in women undergoing COH.