Association between intravenous fluids during labor and primary postpartum hemorrhage: A retrospective cohort study.

INTRODUCTION: There is a major research gap relating to the impact of intravenous (IV) fluids administration during labor on maternal and neonatal outcomes. It is biologically plausible that a relationship between volume of IV fluids and primary postpartum hemorrhage (PPH) exists. The primary objective of this study was to evaluate whether the administration of high-volume IV fluids during labor (≥ 2500 mL) increases the risk of primary PPH and other adverse outcomes for women with a term, singleton pregnancy, in comparison to low-volume IV fluids during labor (<2500 mL). MATERIAL AND METHODS: A retrospective cohort study was conducted at a tertiary referral hospital in Sydney, Australia between 1st September 2021 and 31st October 2022. Inclusion criteria were: women with a live singleton fetus in a cephalic presentation; planning a vaginal birth; and admitted for labor and birth care between 37 and 42 week gestation. The study factor was IV fluids during labor and the primary outcome was primary PPH ≥500 mL. Secondary outcomes included cesarean section and major perineal injury. Pregnancy, birth, and postnatal data were obtained from the hospital's electronic clinical database, electronic medical records, and paper fluid order documentation. Multivariable logistic regression and multiple imputation were used to explore the relationship between volume of IV fluids in labor and PPH. RESULTS: A total of 1023 participants were included of which 339 had a primary PPH (33.1%). There was no association between high-volume IV fluids and PPH after adjusting for demographic and clinical factors (adjusted odds ratio [ORadj]1.02 95% confidence interval [95%CI] 0.72, 1.44). However, there was a positive association between high-volume IV fluids and cesarean section (ORadj 1.99; 95%CI 1.4, 2.8). CONCLUSIONS: The findings of this research are important to further knowledge relating to the administration of IV fluids during labor. The findings emphasize the importance of accurately documenting IV fluids administration and identifies research priorities to enable us to better understand the broader implications of IV fluids administration on pregnancy and perinatal outcomes.