667: Internal monitoring in obese patients: maternal and neonatal outcomes

Abstract

Intrauterine pressure catheters (IUPC) and fetal scalp electrodes (FSE) are commonly used in labor management to aid monitoring. Maternal body habitus limits external monitoring of fetal heart rate and contractions in obese women. The objective of this study was to describe the frequency of internal monitoring in obese patients and investigate maternal and neonatal outcomes associated with use of internal monitors by BMI classification. This was a secondary analysis of a retrospective cohort of all women with a singleton gestation admitted for labor at ≥37 weeks gestation from 2004-2014. The cohort was stratified into 5 groups of BMI classification and frequency of internal monitor use in each BMI group calculated. Primary maternal obstetric outcomes were cesarean delivery and peripartum maternal fever. Neonatal outcomes were 5 minute Apgar <7, neonatal acidemia (umbilical artery pH <7.1), and NICU admission. Outcomes were compared between patients with internal monitors and those without, stratified by obesity (BMI ≥30 kg/m2). Multivariable logistic regression was used to estimate the association between internal monitor use and outcomes while adjusting for confounders. Interaction analysis was used to test whether the relationships between internal monitor use and obstetric outcomes were modified by obesity. Of the total 20,592 patients in cohort, 10,893 (52.9%) were obese. Increasing category of BMI was associated with increasing use of IUPC, FSE, or both (P for trend <0.01; aOR1.42, 95%CI 1.39-1.46; Table 1). Internal monitor use was associated with increased cesarean delivery rate and risk of maternal fever, however these associations were not modified by the presence of obesity (Table 2). Internal monitor use was significantly associated with higher rates of NICU admission among obese patients, but not among non-obese patients (P for interaction 0.02; Table 2). Internal monitor use in obese and non-obese patients was not associated with low Apgars or neonatal acidemia. Internal monitors are used more frequently as patient BMI increases. While internal monitors were associated with an increased risk of maternal fever, obese patients did not appear to have an additional increased risk. These data suggest that obesity alone does not increase the risks associated with internal monitors and that use of IUPC or FSE should not be altered based on BMI alone.View Large Image Figure ViewerDownload Hi-res image Download (PPT)