Impaired fetal growth drives high rates of cesarean delivery after failed trial of labor

Some growth restricted fetuses may not tolerate labor. We performed causal-mediation analysis, an innovative statistical methodology, to quantify the impact of small for gestational age (SGA) birth, a surrogate fetal restriction, and (GA) at delivery on risk cesarean after failed trial labor (TOL). large cross-sectional analysis all para 0 patients who delivered non-anomalous, singleton live births from 22-42 weeks’ gestation in US (2015-2019). The primary outcome was any labor, termed “failed TOL.” exposure SGA birth (sex-specific birthweight < 3rd [SGA3] 5th [SGA5] percentiles GA). causal mediation GA association between (exposure) TOL (outcome). Of 5,422,214 subjects, n=195,123 (3.6%) were SGA3, n=342,315 (6.3%) SGA5, n=4,726,980 (87.2%) AGA. Overall risks weeks higher SGA3 SGA5 (16.9% 15.7%, respectively) compared AGA (14.3%). by strata revealed similar rates versus prior 32 weeks, but notable increased (TABLE 1). Using 39 as reference, that (the controlled direct effect) driver this disparate risk, especially 37-38 41 weeks. Associations (data shown). Compared births, are TOL. This appears be result SGA, delivery. Further study is needed identify with pathologic avoid morbidity TOL.View Large Image Figure ViewerDownload Hi-res image Download (PPT)