EPIDEMIOLOGIC PREDICTORS OF CESAREAN-SECTION IN NULLIPAROUS PATIENTS AT LOW-RISK

OBJECTIVES: We sought to determine whether certain maternal and fetal characteristics influenced the risk of maternal- and fetal-indicated c esarean sections in pregnant women at low risk for adverse perinatal o utcomes. STUDY DESIGN: From a cohort of 6393 low-risk nulliparous pati ents maternal and fetal indicated cesarean section rates with 95% conf idence intervals were calculated and stratified by demographic, anthro pometric, and clinical tests and measurements. The strongest risk fact ors were modeled by means of multiple logistic regression. RESULTS: Fe w risk factors distinguished maternal from fetal characteristics prece ding cesarean delivery. Maternal age was associated with increased ces arean section risk in the tallest group of women only, and cesarean se ction rates decreased with increasing height, increased with higher pr epregnancy weights, and was highest in women carrying male fetuses. Hi gher first prenatal visit diastolic blood pressure, increasing numbers of nonstress tests, greater than or equal to 2+ prenatal urine protei n, late sonograms, geographic region, and practice type were statistic ally significant risk factors as well. Interestingly, results of prena tal visit tests and measurements contributed less to the prevalence of cesarean section than did age, fetal sex, and anthropometric paramete rs. However, the generalizability of these results is limited to low-r isk (predominantly white) populations. CONCLUSIONS: Of the risk factor s we were able to assess, a large proportion of the incidence of cesar ean section in this population of nulliparous patients at low risk was attributable to age, sex of fetus, and anthropometric patient profile s.