Objective: The current study tested the hypothesis that collagen content in the pregnant cervix decreases with labor, using morphologically preserved specimens, avoiding limitations of earlier studies. Collagen abundance remote from pregnancy was also evaluated.
Materials and Methods: Histologic sections of postpartum cervix obtained from 22 cases of total hysterectomy performed immediately after delivery: 13 cases performed after delivery with no labor and 9 cases in which labor had ensued before delivery. Cervices from 10 nonpregnant uteri served as additional controls. Sections were stained, and quantitative histomorphometric assessment of relative collagen abundance was performed using computer-assisted image analysis. Data were assessed for differences using rank sum tests. Relationships between cervical collagen abundance and age, parity, ethnicity, or mode of delivery were also assessed.
Results: Quantitative assessment of collagen abundance in trichrome-stained cervical sections revealed significantly decreased cervical collagen expression in sections from pregnant uteri. Mean percent collagen was 73.5% ± 3.5% (±SEM) in cervices from nonpregnant uteri (n = 10) and 21.5% ± 2.2% in cervices from pregnant uteri (n = 22, p < .0001). Cervical collagen content was significantly lower (p = .04) in cervices from cases in which labor had ensued before delivery (mean percent collagen = 16.1% ± 3.4%, n = 9) than in those in which delivery occurred with no labor (25.3% ± 2.3%, n = 13). No relationships between collagen expression and age, parity, ethnicity, or mode of delivery were observed.
Conclusions: Collagen expression seems to be reduced in the postpartum cervix, particularly after labor has ensued.