The Effect of Chorioamnionitis on Obstetric Delivery Method in a National Population

Background:   Chorioamnionitis is an infection of the placental membranes that is associated with increased risk of maternal and perinatal morbidity.  Chorioamnionitis accounts for 10%- 40% of peripartum febrile morbidity and is associated with 20% - 40% of early neonatal sepsis and pneumonia.  The decision to deliver women with chorioamnionitis by cesarean section is very complicated, involving degree of labor progression, medical and other obstetric indications, patient wishes, and physician preference.

Objective:   To examine the effect of chorioamnionitis on obstetric delivery method by hospital geographic location and hospital type in a national sample. 

Methods:   We performed a cross-sectional study using the 1998-2007 Healthcare Cost and Utilization Project (HCUP) Nationwide Inpatient Sample (NIS).  Delivery type and obstetric and medical indications for cesarean section (CSEC) were identified using International Classification of Diseases, ninth Edition, Clinical Modification (ICD-9-CM) diagnosis and procedure codes.   Logistic regression was used to determine the effect of chorioamnionitis on risk of CSEC delivery, controlling for age, insurance payer, hospital bed size, and obstetric and medical indications for CSEC. 

Results:   A total of 8,416,312 deliveries were identified across the 10 years (6,102,671 (72.5%) vaginal and 2,313,641 (27.5%) CSEC).  The mean age for women having a CSEC and vaginal delivery was 28.7 and 26.9, (t<.001) respectively.  Chorioamnionitis was present in 3.1% of CSEC and 1.3% of vaginal deliveries (P<.001).  When controlling for confounding variables, women with chorioamnionitis were 1.83 times more likely to have a CSEC (CI, 1.75 – 1.94) than women without codes for chorioamnionitis.   Compared to women without chorioamnionitis at an urban/teaching hospital (reference group), women with chorioamnionitis delivered at an urban/teaching hospital were 1.65 times more likely to have CSEC, women with chorioamnionitis at an urban/non-teaching hospital were 2.62 times more likely and women with chorioamnionitis at a rural hospital were 2.79 times more likely to have CSEC (Table 1).  Compared to women without chorioamnionitis in the Midwest (reference group), women with chorioamnionitis in the Northeast region of the U.S. were 2.68 times more likely to have CSEC, women with chorioamnionitis in the South were 2.25 times more likely to have CSEC, women with chorioamnionitis in the Midwest were 1.95 times more likely to have CSEC, and women with chorioamnionitis in the West were 1.89 times more likely to have CSEC (Table 1).

Conclusions:   Women with chorioamnionitis were more likely to have cesarean section delivery than those without chorioamnionitis, and the risk of cesarean section varied by hospital location/teaching status and U.S. region.