Implementation of universal umbilical cord pH analysis in Denmark. A national register-based study

Introduction: Umbilical cord blood gas analysis provides information about intrapartum hypoxia and is considered an important measure of quality in maternity care. Universal measurement of umbilical cord pH (UC-pH), as part of umbilical cord blood gas analysis, has been recommended in Denmark since 2009. The recommendation is that UC-pH is measured from the umbilical cord artery (pH _UA) and vein (pH _UV). The aim of this study was to evaluate the national implementation of universal measurement of UC-pH. Material and methods: The study consisted of two parts. First, an evaluation of the implementation, that is, the proportion of births with measured UC-pH since the recommendation was introduced. Second, an evaluation of the cases in which UC-pH was missing. This analysis only involved births with gestational age ≥35 + 0 weeks. Results: In the period 2009 to 2018 there were 560 889 singleton, live births with registered gestational age in Denmark. The proportion of births with measured pH _UA and pH _UV increased from 12.4% in 2009 to 82.8% in 2015 and then declined to 76.9% in 2018 (p < 0.001). When comparing the group with missing pH from one or both vessels to the group with both pH _UA and pH _UV we found lower occurrence of pregnancy and births complications in the first group, body mass index ≥35 (unadjusted RR: 0.89, 95% CI: 0.85–0.93), pregnancy induced medical conditions (RR: 0.86, 95% CI: 0.84–0.89), fetal distress during birth (RR: 0.77, 95% CI: 0.76–0.79), emergency cesarean section (RR: 0.80, 95% CI: 0.78–0.83) and serious births events (RR: 0.80, 95% CI: 0.74–0.86). In contrast, the occurrence of placental insufficiency (RR: 1.07, 95% CI: 1.03–1.11), small for gestational age (RR: 1.36, 95% CI: 1.30–1.43, for <2.3th percentile), hypothermia treatment (RR: 1.60, 95% CI: 1.21–2.14) and neonatal death (RR: 1.96, 95% CI: 1.40–2.74) were higher in the group without measured pH _UA and pH _UV. Conclusions: The use of UC-pH measurement has increased markedly in Denmark since universal measurement was recommended in 2009. Missing UC-pH from one or both vessels was associated with less complicated pregnancies and with small for gestational age, hypothermia treatment and neonatal death.