Three-quarters of the ocean crust formed at fast-spreading ridges is composed of plutonic rocks whose mineral assemblages, textures and compositions record the history of melt transport and crystallization between the mantle and the seafloor.Despite the significance of these rocks, sampling them in situ is extremely challenging due to the overlying dikes and lavas. This means that our models for

OBJECTIVE The objective was to estimate the effect of vaginal childbirth and other obstetric exposures on pelvic muscle strength 6–11 years after delivery and to investigate the relationship between pelvic muscle strength and pelvic floor disorders. METHODS Among 666 parous women, pelvic muscle strength was measured with a perineometer 6–11 years after delivery. Obstetric exposures were classified by review of hospital records. Pelvic floor outcomes, including stress incontinence, overactive bladder, anal incontinence, and prolapse symptoms, were assessed with a validated questionnaire. Pelvic organ support was assessed using the Pelvic Organ Prolapse Quantification system. Kruskal-Wallis tests were used to estimate the univariable associations of obstetric exposures and pelvic floor outcomes with peak muscle strength. Stepwise multivariable linear regression models were used to estimate the association between obstetric exposures and muscle strength. RESULTS In comparison with women who delivered all of their children by cesarean, peak muscle strength and duration of contraction were reduced among women with a history of vaginal delivery (39 compared with 29 cm H2O, P<.001). Pelvic muscle strength was further reduced after history of forceps delivery (17 cm H2O, P<.001). After vaginal delivery, reduced pelvic muscle strength was associated with symptoms of anal incontinence (P=.028) and pelvic organ prolapse on examination (P=.025); these associations were not observed among those who had delivered exclusively by cesarean. CONCLUSION Pelvic muscle strength almost a decade after childbirth is affected by vaginal delivery and by forceps delivery. Although statistically significant, some of the differences observed were small in magnitude.