Effect of pethidine administered during the first stage of labor on the acid–base status at birth

ObjectiveTo evaluate the association between the use of pethidine during the first stage of labor and the presence, type and timing of acidosis in the newborn at birth.Study designSecondary data analysis of a randomized controlled trial, which included term singleton pregnancies diagnosed with dystocia and requiring active management of labor. Women were randomized to receive either 100 mg of pethidine or placebo. Statistical analyses were performed using χ2 or Fisher's exact tests for proportions and multiple linear regression for continuous outcomes.ResultsThree hundred and eighty-three pregnant women with a valid arterial blood cord sample were included in the final analysis. Lower pH and bicarbonate levels, as well as higher pCO2 levels were found in the pethidide group. A higher incidence of acidosis was found in the pethidine group (pH < 7.12 OR: 8.59 95% C.I. 3.29, 22.46). The highest frequency of acidosis was encountered when pethidine-delivery interval was 5 h.ConclusionPethidine use during the first stage of labor was associated with an increased risk of acidosis at birth.