Umbilical Cord Blood Gas in Newborns with Prenatal Diagnosis of Congenital Heart Disease: Insight into In-Utero and Delivery Hemodynamics

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Umbilical Cord Blood Gas in Newborns with Prenatal Diagnosis of Congenital Heart Disease: Insight into In-Utero and Delivery Hemodynamics.

Adams AD, Aggarwal N, Iqbal SN, Tague L, Skurow-Todd K, McCarter R, Donofrio MT.

Pediatr Cardiol. 2019 Dec;40(8):1575-1583. doi: 10.1007/s00246-019-02189-x. Epub 2019 Aug 30.

PMID: 31471626

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Take Home Points:

  • Newborns with a prenatal diagnosis of congenital heart disease are not at increased risk of acidosis at the time of delivery when compared to gestational age-matched controls.
  • No difference was noticed in the umbilical arterial (UA) pH between those with single ventricle vs two-ventricle disease and those with and without aortic arch obstruction.
  • In pregnancies complicated by congenital heart disease, spontaneous vaginal delivery with prolonged labor seems to impact the fetal outcome as noted by the significant decline in UA pH with increasing duration of labor in this group when compared to other modes such as induced vaginal delivery and C-Section post-labor.

Commentary from Dr. Venu Amula (Salt Lake City), section editor of Fetal Cardiology Journal Watch: The American College of Obstetricians and Gynecologists and the American Academy of Pediatrics recommend performing umbilical artery blood acid-base analysis after certain high-risk deliveries in which a fetal metabolic abnormality is suspected to assess fetal well-being. Adams et al conducted this single-center, retrospective observational study to determine if newborns with congenital heart disease are at a higher risk for acidosis at delivery as determined by the umbilical cord blood analysis. The control group included singleton deliveries without CHD matched by date of birth and gestational age. The authors also sought to determine if specific fetal cardiac diagnosis, type, and duration of labor are associated with acidosis. The cases included all forms of complex congenital heart disease. Given the unique physiological challenges faced by single ventricle heart lesions and those with systemic outflow obstruction – the lesions were divided into 4 categories – Single Ventricle lesions with and without aortic arch obstruction, and Biventricular lesions with and without aortic arch obstruction. Class, I was defined as patients with two ventricles without aortic arch obstruction Class II as patients with two ventricles with arch obstruction, Class III as patients with a single ventricle without arch obstruction and Class IV as patients with a single ventricle with arch obstruction.

The study cohort consisted of 134 cases with an equal number of gestational and calendar year matched healthy newborns. Overall there was no difference in the median UA pH in the cases with congenital heart disease versus the control group. There was also no difference by physiological class nor by single ventricle vs two ventricle type nor by the presence or absence of aortic arch obstruction. The authors conclude that fetuses with congenital heart disease have well-compensated hemodynamics and inutero oxygen delivery owing to fetoplacental circulation regardless of the subtype of congenital heart disease.

They also evaluated the effect of mode of delivery on UA pH and found that in the congenital heart disease group there was a significant decline in the median UA pH with increasing duration of labor in those with spontaneous vaginal delivery when compared to those with induced vaginal and C-Section Post-Labor. However, it is to be noted that even in this group pathological fetal acidemia, a practical pH threshold where neonatal morbidity increases i.e. umbilical artery pH <7, was rare.

The study is limited by a sampling bias given no umbilical arterial blood analysis data was present for those with hemodynamically unstable neonates with congenital heart lesions. Maternal characteristics were also not completely matched given the placental health may impact umbilical cord gas analysis even though venous sampling would be more reflective of that.

Duration of labor in fetuses with the diagnosis of congenital heart disease planned for spontaneous vaginal delivery may impact the outcome as evidenced by declining UA pH and needs planned perinatal management.

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