B 2 U CS - 三三三= = =,=,= = X ESTIMATING RISK IN COHORT STUDIES & MORE ON RISK Context: An epidemiologist theorizes that women who are put on medically ordered bed-rest during pregnancy may experience higher rates of muscular back injury (compared to mothers with healthy pregnancies) during the first year post-partum as a result of loss of muscle tone related to the bed-rest, combined with the physical demands of childcare. You design a cohort study to evaluate this association Exposure: Women are considered exposed if they are put on medically-ordered bed-rost for period of one month or longer during their pregnancy, Women who are not put on bed-restor who are put on shorter periods of bed-rest are considered to be unexposed. Outcome: Women are considered to have the outcome in question if they experience any injury to the back during the first year postpartum that requires medical evaluation and results in an official diagnosis of muscular injury, Women who experience back pain or soreness that does not require evaluation or who have different types of diagnosed back injuries (non-muscular) do not have the outcome. Study Population: You obtain informed consent and recruit 184 women at their first prenatal appointments at the 3 largest ob-gyn clinics in the Providence medical system in Portland. After following the recruited women over the course of their
pregnancies and through the first year of study, you obtain the following data. Of the original 184 women recruited, 8 are lost to follow-up, and 3 experience early miscarriage and are dropped from the study. Among all mothers included in the final analysis, the cumulative incidence of muscular back injury is 38%. A total of 48 women in the final analysis met the exposure criteria of bed-rest, 29 of whom experienced the outcome of interest. Questions: 1. Draw and complete a 2 x 2 table expressing this data, including row and column totals: OUTCOME OUTCOME EXPOSURE BACK INJURY NO BACK INJURY TOTAL BED REST NO BED REST TOTAL
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