Internal fetal and uterine monitoring in obese patients and maternal obstetrical outcomes

Antonina I. Frolova, Molly J. Stout, Ebony B. Carter, George A. Macones, Alison G. Cahill, Nandini Raghuraman

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Background: The maternal habitus in the setting of obesity makes external monitoring of the fetal heart rate and contractions suboptimal, and internal monitors may be utilized more often in this population. Obesity is a risk factor for obstetrical infectious complications, but it is unknown whether the use of internal monitors in this population is associated with additional risks. Objective: This study aimed to investigate the association between the use of an intrauterine pressure catheter and a fetal scalp electrode and maternal infectious morbidity among women with obesity. Study Design: This secondary analysis of a prospective cohort study included women with singleton gestations admitted for labor at ≥37 weeks’ gestation at a tertiary care institution from 2010 to 2014. Obesity was defined as a body mass index of ≥30 kg/m2. The primary outcome was a composite maternal infectious morbidity, which included peripartum maternal fever, chorioamnionitis, and endomyometritis. Secondary outcomes were cesarean delivery and individual components of the maternal infectious composite. Multivariable logistic regression was used to compare the rates of infectious maternal morbidity, cesarean delivery, or operative vaginal delivery between patients with and without internal monitors, while adjusting for the confounders. An interaction term was included in the logistic regression models to test whether the relationship between the internal monitors and cesarean delivery or infectious morbidity was modified by the presence or absence of obesity. Results: Of the 8482 women who met the inclusion criteria for the study, 4727 (55.7%) had obesity and 3755 (44.3%) did not have obesity. The women with obesity were more likely to have internal monitors placed during labor than those without obesity (65.4% vs 50.5%; P<.001). The use of internal monitors was associated with an increased risk for the composite maternal infectious morbidity (9.9% vs 4.1%; P<.01 and adjusted odds ratio, 2.08; 95% confidence interval, 1.70–2.55). Women with obesity had a weaker association between the use of internal monitors and maternal infectious morbidity than women without obesity (P value for interaction of.02). The incidence of cesarean delivery was also significantly higher among women who had internal monitors placed during their labor course (adjusted odds ratio, 2.84; 95% confidence interval, 2.46–3.28), and this interaction was not modified by obesity. Conclusion: Although a higher proportion of women with obesity have internal monitors placed during their labor course, they are not more susceptible to maternal infectious morbidity as a result of internal monitor use. Providers should not limit the necessary internal monitor use in women with obesity on the basis of concerns for maternal infectious morbidity.

Original languageEnglish
Article number100282
JournalAmerican journal of obstetrics & gynecology MFM
Issue number1
StatePublished - Jan 2021


  • internal monitor
  • labor
  • maternal obesity
  • obstetric morbidity


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