Histochemical Assessment of Reticulin-Collagen Patterns in the Mid-Secretory Endometrium Predicts Recurrent Pregnancy Loss.

Background/objectives: Normal remodeling of the extracellular matrix of the endometrium is a necessary condition for the implantation of a blastocyst. We evaluated whether the use of histochemical reticulin-collagen staining can improve the assessment of the extracellular matrix of the mid-secretory endometrium in recrudescent clinical/biochemical pregnancy losses in comparison with ultrasound and routine histological examination.

Methods: We compared the histochemical pattern of reticulin-collagen endometrial biopsy (21st day of the cycle) with ultrasonography and standard histological examination of the endometrium in the following groups: (1) fertile women with gravidity ≥ 2, (gravidity = parity) and (2) women with two or more clinical/biochemical pregnancy losses.

Results: A normal pattern (NP) with ordered reticulin fibers forming cellular structures was determined in 92% of biopsies with physiological reproductive status and 44% of biopsies with recrudescent reproductive failure (p < 0.05), despite the fact that there were no differences in ultrasonography and standard histological examination between the groups (p > 0.05). A histochemical pattern of insufficient secretory endometrial transformation with abnormal noodle-like pattern (aNP) collagen fibers was more common in recrudescent reproductive failure (56%) than in women with physiological reproductive status (8%) (p < 0.001), despite the fact that insufficient secretory endometrial transformation with an abnormal noodle-like pattern with collagenization (aNPC) was detected only in recrudescent reproductive failure, and it was not detected in women with physiological reproductive status (p < 0.00001).

Conclusions: We determined the histochemical pattern of the extracellular matrix of the endometrium in terms of the type of reticulin-collagen, associated in our study with recrudescent clinical/biochemical pregnancy loss, with improved predictability compared to ultrasonography and standard histological examination. We propose to use the method of histochemical evaluation of the reticulin-collagen pattern in order to stratify groups of women of fertile age at risk of reproductive failure.