The Association of Fetal Acidemia With Adverse Neonatal Outcomes at Time of Scheduled Cesarean Delivery

Abstract

Up to 30% of term labor deliveries experience fetal acidemia, a condition usually caused by hypoxia that is associated with adverse neonatal outcomes. The American College of Obstetricians and Gynecologists and American Academy of Pediatrics recommend assessing fetal umbilical artery (UA) blood gases at delivery when fetal metabolic status is in question. Although a UA pH of 7.24 to 7.28 is considered normal, the degree of acidemia associated with neonatal death is unclear. Recent data suggest that mild acidemia (UA pH of 7.0–7.2) and certain types of acidemia (metabolic, mixed, or respiratory) also indicate increased risk for adverse outcomes. Most cases of acidemia follow labor when the placental gas exchange is interrupted during contractions. But fetal acidemia is rare in cases of scheduled prelabor cesarean delivery (CD) and not well described in the literature. This study aims to determine if fetal acidemia at the time of scheduled, prelabor CD is associated with neonatal morbidity.This was a retrospective cohort study comparing patients with and without fetal acidemia, defined as a UA pH <7.2. Included were singleton neonates delivered via scheduled CD at a single tertiary care center from June 2004 to December 2014. Excluded were those who delivered before 37 weeks of gestation, were diagnosed with major anomalies, or underwent CD due to labor, rupture of membranes, or nonreassuring fetal status. Also excluded were cases in which data on validated umbilical cord gases were unavailable. The primary outcome was a composite of neonatal outcomes, including neonatal death, encephalopathy, therapeutic hypothermia, seizures, intubation, and respiratory distress.A total of 2081 neonates met the inclusion criteria, with fetal acidemia present at the time of delivery in 252 cases (12.1%). Acidemia occurred more frequently in breech neonates and those born to mothers with gestational diabetes mellitus or obesity. Intraoperative maternal hypotension, use of vasopressor therapy, and increased times from anesthesia induction and skin incision to delivery were also more likely to occur in cases of acidemia. The primary composite outcome was observed in 176 (8.5%) of neonates. This outcome was significantly higher in those with acidemia than those without (7.6% vs 15.1%; adjusted risk ratio [aRR], 2.95; 95% confidence interval [CI], 2.03 to 4.12). Intubation (aRR 3.50; 95% CI, 1.27–9.13) and respiratory distress (aRR, 2.93; 95% CI, 2.00–4.13) also occurred more frequently among those with acidemia. As the rate of UA pH categories decreased, the proportion of neonates with the primary outcome increased: 13.5% morbidity if UA pH was 7.0 to 7.19 versus 42.9% morbidity if UA pH was <7.0. Compared with neonates with a UA pH ≥7.2, the risk for adverse outcomes rose 3.2-fold in those with a UA pH <7.1 (aRR, 3.23; 95% CI, 1.73–5.24) and 6.6-fold in those with a UA pH <7.0 (aRR, 6.64; 95% CI, 3.23–8.96). The primary outcome was observed in 24.7% of neonates with respiratory acidemia, 27.5% with mixed, and 25% with other ac...

Spinal Hypotension and Time from Spinal-to-Delivery in Scheduled Cesarean Deliveries: Association with Neonatal Acidosis

“…4 Bligard et al conducted a single-center retrospective study from 2004 to 2014 examining the association of fetal acidemia with adverse neonatal outcomes in scheduled CD, and the authors reported vasopressor use at a rate of 71.9%. 2 Rimsza et al described a higher rate of vasopressor administration in a population who underwent scheduled CD at a tertiary care center between 2014 and 2017. Notably, the authors also reported a large proportion of patients with spinal-induced hypotension—with 91.3% of individuals having a documented mean arterial pressure (MAP) > 20% below baseline despite upwards of 90% receiving vasopressors.…”

“…The primary outcome was neonatal acidosis defined as an umbilical artery pH ≤ 7.1 or base excess ≤ −12 mmol, as previous studies have shown increased risk of adverse outcomes in neonates at these thresholds. 2 9 10 11 12 Secondary outcomes were composites of neonatal and maternal adverse outcomes. The composite neonatal adverse outcome (CNAO) included any of the following: neonatal death, Apgar score < 7 at 5 minutes, neonatal intensive care unit (NICU) admission > 12 hours, intubation, respiratory support > 6 hours, seizures, sepsis, HIE, or therapeutic hypothermia.…”

“…7 8 Even mild acidosis—defined as an umbilical artery pH of 7.1 to 7.2—has been associated with adverse neonatal outcomes like respiratory distress, need for mechanical ventilation, sepsis, HIE, and need for therapeutic hypothermia. 2 9 10 11 12 With scheduled CD, studies have identified maternal hypotension after spinal anesthesia and the time from spinal-to-delivery as two factors independently associated with an increased risk for neonatal acidosis. 2 4 5 Current published data, however, have several limitations.…”

“…They do not include the widespread adoption of prophylactic vasopressor infusions before spinal anesthesia, and many report high rates of spinal hypotension, ranging from 40 to 90%. 2 5 13 Furthermore, most studies do not account for the duration of hypotension when assessing its effects on perinatal outcomes, only accounting for its occurrence or magnitude alone. 2 5 13 There is also a lack of data on maternal morbidity due to hypotension after spinal anesthesia in scheduled CD.…”

“…Neonatal acidosis has been reported in 2 to 15% of scheduled CDs depending on the threshold selected to define it. 2 3 4 5 6 Neonatal acidosis is associated with end organ damage, seizure, hypoxic–ischemic encephalopathy (HIE), and death. 7 8 Even mild acidosis—defined as an umbilical artery pH of 7.1 to 7.2—has been associated with adverse neonatal outcomes like respiratory distress, need for mechanical ventilation, sepsis, HIE, and need for therapeutic hypothermia.…”