Pregnancy and parturition negatively impact vaginal angle and alter expression of vaginal MMP-9.

BACKGROUND: Parity is the greatest risk factor for the development of pelvic organ prolapse. The normally supported vagina is pulled up and back over the levator ani. Loss of vaginal angulation has been associated with prolapse and may represent injury to the vaginal supportive tissues. OBJECTIVE: We proposed and examined the following hypotheses: (1) pregnancy and delivery impact vaginal support, leading to loss of vaginal angle; (2) vaginal angulation is restored postpartum; and (3) uncomplicated vaginal delivery (VD) is associated with accelerated remodeling of the vaginal fibrillar matrix. MATERIALS AND METHODS: We prospectively enrolled a cohort of nulliparas in the first trimester of pregnancy, and abstracted demographic and delivery data. Metalloproteinase 9 (MMP-9) activity in the vagina was determined in the first and third trimesters and 1 year postpartum using a substrate activity assay. Uncomplicated VD was defined as none of the following: cesarean delivery, forceps or vacuum use, shoulder dystocia, obstetric anal sphincter laceration, or prolonged second-stage labor. Women were grouped dichotomously for comparison based on this definition. A subset of participants underwent transperineal ultrasound. RESULTS: We enrolled 173 women with mean age of 25 ± 6 years and a body mass index of 20 ± 7 kg/m2. Of the women, 67% identified as white/Caucasian, 27% black/African American, or 6% Hispanic/Latina. The mean delivery age was 39 ± 3 weeks, with 59% of participants experiencing uncomplicated VD. The MMP-9 median activity (ng/mg protein) was 242.0 (IQR, 18.7, 896.8; n = 157) in the first trimester, 130.8 (IQR, 14.6, 883.8; n = 148) in the third trimester, and 463.5 (IQR, 92.2, 900.0; n = 94) postpartum. The MMP-9 activity increased between the third trimester and 1 year postpartum (P = .006), with no significant difference between MMP-9 values in the first and third trimesters (P = .674). The vaginal angle became less acute from the first to the third trimester, and this change persisted postpartum. The vaginal angulation over the levator plate became more acute between the third trimester and postpartum in women who experienced uncomplicated VD compared to those who did not (-6.4 ± 22.1 degrees vs 17.5 ± 14.8 degrees; P = .017). Higher MMP-9 activity postpartum was associated with uncomplicated VD, with 67% of women in the third tertile achieving uncomplicated VD versus 39% in the first tertile (P = .029). CONCLUSION: Loss of vaginal angulation occurs between trimesters, and women do not recover their baseline resting angle postpartum. MMP-9 activity increases postpartum. Women experiencing uncomplicated VD demonstrate higher postpartum MMP-9 activity and are more likely to have recovered their vaginal angle.

Maternal adaptations in preparation for parturition predict uncomplicated spontaneous delivery outcome.

OBJECTIVE: The objective of the study was to define maternal tissue adaptations in pregnancy associated with uncomplicated spontaneous vaginal delivery using anatomical and biological outcomes. STUDY DESIGN: Nulliparous gravidas were prospectively enrolled in the first trimester at 2 institutions. Demographic and delivery data were chart abstracted. Vaginal elastase activity (units per milligram of protein) and Pelvic Organ Prolapse Quantification measurements of pelvic organ support were obtained in the first and third trimesters. A subset underwent 3-dimensional ultrasound measures of levator hiatus. Uncomplicated spontaneous vaginal delivery (VD) was defined as no cesarean, forceps, vacuum, shoulder dystocia, third- or fourth-degree perineal laceration, or prolonged second stage labor. RESULTS: We enrolled 173 women in their first trimester, 50 of whom had ultrasounds. Mean age was 25.5 ± 5.5 years with a body mass index of 28.0 ± 7.3 kg/m(2). Sixty-seven percent were white/Caucasian, 27% black/African American, and 6% Hispanic/Latina. Mean delivery gestational age was 38.5 ± 2.9 weeks, with 23% delivering by cesarean and 59% achieving uncomplicated spontaneous VD. Vaginal support changed significantly over trimesters with posterior vaginal and hiatal relaxation, vaginal lengthening, and increased levator hiatus area during strain. Women achieving uncomplicated spontaneous VD demonstrated significantly greater relaxation on third-trimester Pelvic Organ Prolapse Quantification for anterior, apical, and hiatal measures than those without uncomplicated spontaneous VD. Higher first-trimester vaginal elastase activity was strongly associated with uncomplicated spontaneous VD (geometric mean activity 0.289 ± 0.830 U/mg vs -0.029 ± 0.585 U/mg, P = .009). Higher first-trimester elastase, younger age, lower first-trimester body mass index, and more third-trimester vaginal support laxity in points C and GH were predictive of VD success. CONCLUSION: Significant maternal adaptations occur in the vagina during pregnancy, presumably in preparation for vaginal delivery. Greater adaptation, including vaginal descent and higher first-trimester elastase activity, is associated with an increased likelihood of uncomplicated spontaneous VD.