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

BACKGROUND: Childbirth experience is an increasingly recognized and important measure of quality of obstetric care. Previous research has shown that it can be affected by intrapartum care and how labor is followed. A partograph is recommended to follow labor progression by recording cervical dilation over time. There are currently different guidelines in use worldwide to follow labor progression. The two main ones are the partograph recommended by the World Health Organization (WHO) based on the work of Friedman and Philpott and a guideline based on Zhang\'s research. In our study we assessed the effect of adhering to Zhang\'s guideline or the WHO partograph on childbirth experience. Zhang\'s guideline describes expected normal labor progression based on data from contemporary obstetric populations, resulting in an exponential progression curve, compared with the linear WHO partograph. The choice of labor curve affects the intrapartum follow-up of women and this could potentially affect childbirth experience.
METHODS: The Labor Progression Study (LaPS) study was a prospective, cluster randomized controlled trial conducted at 14 birth centers in Norway. Birth centers were randomized to either follow Zhang\'s guideline or the WHO partograph. Nulliparous women in active labor, with one fetus in cephalic presentation at term and spontaneous labor onset were included. At 4 weeks postpartum, included women received an online login to complete the Childbirth Experience Questionnaire (CEQ). Total score on the CEQ, the four domain scores on the CEQ, and scores on the individual items on the CEQ were compared between the two groups.
RESULTS: There were 1855 women in the Zhang group and 1749 women in the WHO partograph group. There was no difference in the total or domain CEQ scores between the two groups. We found statistically significant differences for two individual items; women in the Zhang group scored lower on positive memories and feeling of control.
CONCLUSIONS: Based on our findings on childbirth experience there is no reason to prefer Zhang\'s guideline over the WHO partograph.