Concerns about the contemporary labor curves and guidelines: Is it time to revisit the old ones?

Abstract

Background: One of the main reasons for the rising caesarean section rate is labor progression abnormalities. New guidelines were released promoting the changing paradigm from Friedman to Zhang's labor curves. However, the lack of evidence of its safety and the unclear effect on caesarean section rates have been challenging its adoption.

Objective: Comparison between women with Friedman's criteria of arrested labor and women with Zhang's in terms of maternal and neonatal outcomes.

Materials and methods: Retrospective, single-center cohort study in a tertiary hospital between January 1st 2015 and December 31st of 2016.

Exclusion criteria: preterm or multiple deliveries, women without entering the active stage of labor, scheduled caesarean deliveries. Women were classified into 3 groups: normal progress, labor arrest by Friedman's criteria or by Zhang's criteria. Maternal morbidity included thrombotic, hemorrhagic, traumatic, infectious, and "total" (any of the previous morbidities). Adverse neonatal outcomes were assessed as a composite. Single and multivariable logistic regression was used to obtain the odd ratio (ORs) of each group and by stage of labor. Statistical significance threshold was set at 0,05.

Results: From a total number of 5051 deliveries, 3665 deliveries were included in the study, 2839 with normal labor progression, 426 with labor arrest according to Friedman's criteria and 400 according to Zhang's criteria. Regarding neonatal outcomes, no significant differences were observed. Compared to normal labor, labor arrest was significantly associated with higher total maternal morbidity (OR for Friedman's criteria 3.04; 95% confidence interval, 2.26-4.09; OR for Zhang's criteria 3.59; 2.68-4.80), maternal hemorrhagic (OR for Friedman's criteria 2.87; 1.81-4.55; OR for Zhang's criteria 2.80; 1.75-4.49) and infectious morbidity (OR for Friedman's criteria 3.56; 2.44-5.18; OR for Zhang's criteria 4.77; 3.34-6.80). Results were still significant after adjustment for confounders. Comparing Friedman's and Zhang's criteria, no significant differences regarding maternal and neonatal outcomes were verified.

Conclusion: Changing criteria of labor arrest from Friedman's to Zhang's was not associated with more maternal morbidity in our study population nor worse neonatal outcomes. Changing labor arrest criteria from Friedman's to Zhang's may reduce caesarean section rates without an important increase in maternal and neonatal morbidities.

Keywords: Friedman labor curves; Labor arrest; Labor progression; Zhang labor curves.