Elevated liver enzymes and adverse outcomes among patients with preeclampsia with severe features

The rate of preeclampsia with severe features has increased. Previous studies have shown elevated liver enzymes are an indicator of worsening hypertensive disease of pregnancy and adverse outcomes, therefore leading to their inclusion as a diagnostic criterion for severe features of preeclampsia. Despite this, there are limited data to support an aspartate aminotransferase (AST) or alanine aminotransferase (ALT) concentration ≥ two times the upper limit of normal as the critical point at which maternal harm from ongoing pregnancy exceeds neonatal harm from delivery. The objective of this study is to evaluate the association between elevated liver enzymes and maternal and neonatal outcomes among patients with preeclampsia with severe features.

Retrospective cohort study among hypertensive patients who delivered ≥23 weeks' gestation at Oregon Health & Science University (October 2013-September 2018). Those with preeclampsia with severe features (including chronic hypertension with superimposed preeclampsia meeting criteria for severe features) were included after a screening of ICD-9 and ICD-10 codes and chart validation. The primary exposure was elevated liver enzymes prior to delivery, according to the American College of Obstetricians and Gynecologists' criteria for severe features of preeclampsia: aspartate aminotransferase (AST) or alanine aminotransferase (ALT) ≥2x the upper limit of normal (above threshold liver function tests [LFTs]). Primary outcomes included adverse maternal and neonatal outcomes. Differences were analyzed by Chi-squared, Fisher's exact, t-test, and logistic regression, with α = 0.05.

Of 11,825 deliveries, 319 (2.7%) met inclusion criteria and had preeclampsia with severe features. Of these, 44 (13.8%) had above threshold LFTs. Adverse maternal outcomes were no different in those with above threshold LFTs compared to those with below threshold LFTs. The unadjusted odds of an adverse neonatal outcome were 2.08 times greater in patients with above threshold LFTs (95% CI: 1.04-4.14), and 2.43 times greater when adjusting for maternal characteristics (95% CI: 1.17-5.04) compared to those with below threshold LFTs. However, the association between above threshold LFTs and adverse neonatal outcomes became non-significant after adjustment for gestational age at delivery (OR: 1.54, 95% CI: 0.63-3.76).

Among patients with preeclampsia with severe features, above threshold LFTs are not independently associated with an increased risk of adverse maternal or neonatal outcomes. Adverse neonatal outcomes in patients with preeclampsia with severe features and above threshold LFTs are driven by earlier gestational age at delivery. Prospective studies are needed to guide delivery timing in patients with preeclampsia and elevated liver enzymes.

The criteria for elevated liver function tests (greater than two times the upper limit of normal) are widely accepted among obstetricians to diagnose a severe feature of preeclampsia. However, these criteria are based on expert opinion and extrapolated from data on patients with HELLP syndrome. Since preterm delivery of the neonate is recommended for preeclampsia with severe features, the threshold used to define severe liver enzyme elevation has a direct impact on neonatal outcomes. Therefore, the goal of our study was to determine if patients with preeclampsia with severe features and a pre-delivery AST or ALT level ≥ two times the upper limit of normal have worse maternal and neonatal outcomes compared to those with an AST and ALT below this level.