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

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.

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.

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 .

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.