Evaluation of alanine aminotransferase/aspartate aminotransferase ratio and high-density lipoprotein for predicting neonatal adverse outcomes associated with intrahepatic cholestasis of pregnancy

Study participants

This retrospective study consisted of 147 pregnant women diagnosed ICP and 120 normal pregnant women who came to The Fourth Hospital of Shijiazhuang, China, for obstetric examination between December 2016 to December 2022. All pregnant women and their families were informed in detail about the purpose of the experiment and signed informed consent at the time of enrolment. The study was approved by the Ethics Review Committee of The Fourth Hospital of Shijiazhuang (No.20230034) and all the researchers collected data in strict accordance with the ethical requirements throughout the study. Eligible participants were women aged 18-45; singleton natural pregnancy; without diabetes, hepatobiliary diseases, immunological diseases or other pregnancy complications; pregnant women were conscious and able to cooperate with the study and the data of the enrolled cases were complete. The exclusion criteria: pregnant women with combined psychiatric disorders; pregnant women with biliary obstruction and other gallbladder diseases; patients with hypothyroidism or subhypothyroidism, complicated intrauterine infections and other complications affecting the outcome of the study.

Data collection

The sociological information and basic characteristics of all pregnant women were obtained by questionnaire, including age, height, pre-pregnancy weight, number of births, etc. The gestational week was determined by last menstrual period and/or ultrasonographic measurements, and the condition of the newborn was obtained by consulting delivery record and newborn care records. All blood samples were fasted for more than 8 h and collected at the same time in the morning under aseptic conditions, after which they were centrifuged at 3,000 r/min by a laboratory physician (Luo et al., 2022). The liver function and blood lipid levels were measured using a fully automated biochemical analyzer (Cobas 701; Roche, Basel, Switzerland). Adverse pregnancy outcomes included caesarean section, preeclampsia (Sinkey et al., 2020) (SBP ≥ 140 mmHg and/or DBP ≥ 90 mmHg with urinary protein ≥0.3g/24 h or random urine protein), premature rupture of membranes (PROM) (Ronzoni et al., 2022), meconium-stained amniotic fluid (MSAF) (Estiú et al., 2017), postpartum hemorrhage (Schlembach et al., 2014) (≥500 mL for vaginal deliveries and ≥1000 mL for deliveries by caesarean section), preterm (gestational age < 37 weeks), neonatal hypoglycemia (blood glucose < 2.2 mmol/L), neonatal respiratory distress (Bricelj et al., 2017), neonatal hyperbilirubinemia (Maisels et al., 2009), and cardiac injury.

Diagnosis of ICP

ICP is diagnosed when the level of TBA in a pregnant woman increases by ≥ 10 µmol/L during pregnancy. Patients were classified as having mild or severe cholestasis based on TBA concentrations of 10–40 or ≥ 40 µmol/L, respectively (Mays, 2010; Liu et al., 2015).

Statistical analysis

Data were collected as previously study described in Fan et al. (2024). Specifically, statistical analysis of the data was carried out using SPSS 22.0 software. Continuous variables were described by median (range), and frequencies (percentages) were described as categorical variables. The Mann–Whitney U test was used to analyze the differences between non-normal continuous variables and the chi-square test was used to compare the differences between categorical variables. Binary logistic regression analysis was used to evaluate the relationship between adverse pregnancy outcomes and ALT, AST, ALT/AST, and HDL respectively. The association between the levels of the above indicators and the incidence of adverse pregnancy outcomes were evaluated by odds of exposure (OR) and 95% confidence intervals (CI) to assess the precision of the point estimates. The receiver operating characteristic (ROC) curves for ALT/AST independently and combined with HDL were both drawn, and the sensitivity and specificity were calculated according to ROC curves. All statistical analyses with significant differences were considered to be p < 0.05.

Study population description

According to their serum total bile acid (TBA) levels, 147 pregnant women with ICP had TBA levels ≥10 µmol/L were participate in the study, of which 122 mild ICP women had TBA levels of 10-39.9 µmol/L, and 25 severe ICP women had TBA levels ≥40 µmol/L. 120 normal pregnant women with TBA level <10 µmol/L during the same period were selected as the control group. The general information of 267 included pregnant women were shown in Table 1. The characteristics of enrolled pregnant women such as age, pre-pregnancy BMI, reproductive history, and the gender of neonates had no significant differences. The neonatal birth weight in pregnant women with ICP was significantly lower than those in normal pregnant women (p < 0.05). We found the gestational week in the mild and severe ICP women were all significantly lower compared to the normal group (p < 0.05) and the gestational age at diagnosis in the severe ICP group was also lower than in the mild ICP group (p < 0.05). Although there was no significant difference in gestational weight gain (GWG) between ICP and normal pregnant women, a lower GWG was detected in the severe ICP women than in the mild ICP group (p < 0.05).

Comparison of biochemical indices of mild ICP, severe ICP and normal pregnant women

We compared the laboratory biochemical indices among the mild ICP group, the severe ICP group and the normal group in Table 2. We found lower levels of total protein (TP) and albumin (ALB), and the blood urea nitrogen (BUN), serum creatinine (CR) and uric acid (UA) levels were higher in the ICP group compared to the normal group (all p < 0.05). We also detected the significantly higher levels of TBIL, DBIL and IBIL in the severe ICP group than in the mild ICP group (all p < 0.05). To our surprise, although the levels of TG, TC and LDL were not significantly different in the normal, mild ICP and severe ICP groups (p > 0.05), we discovered significant differences levels of AST, ALT, AST/ALT, A/G and HDL not only in the normal and ICP groups, but also in the different TBA levels of ICP groups. In particular, in Supplemental Information 1, increasing TBA level was associated with higher AST, ALT, ALT/AST and lower HDL level (all p < 0.05).

Comparison of pregnancy outcomes between mild and severe ICP and normal pregnant women

As shown in Table 3, except for postpartum hemorrhage, the rate of adverse maternal pregnancy outcomes such as cesarean section, preeclampsia, PROM, and MSAF in the ICP group were all significantly different from those in the normal group (all p < 0.05), and the significant differences of cesarean section, preeclampsia, and MSAF were also found between the mild ICP group and severe ICP group (all p < 0.05). Comparison of neonatal outcomes between normal and ICP groups revealed significant differences in neonatal preterm, hypoglycemia, respiratory distress, hyperbilirubinemia, and cardiac injury (all p < 0.05). Surprisingly, as maternal TBA levels increased, there were obvious higher rate of neonatal preterm [31(25.4%) vs. 13 (52.0%), (p = 0.008)], hyperbilirubinemia [32 (26.2%) vs. 13 (52.0%), (p = 0.011)] and cardiac injury [21 (17.2%) vs. 9 (36.0%) (p = 0.034)] in the severe ICP group than in the mild ICP group.

Associations between biochemical indices and adverse outcomes of maternal and neonatal

ICP causes liver function injury and lipid metabolism disorders in pregnant women, which not only increases the incidence of adverse maternal outcomes (Menzyk et al., 2018; Zhan et al., 2022), but also has a serious impacts on fetal development (Estiú et al., 2017; Pillarisetty & Sharma, 2023; Koh, Kathirvel & Mathur, 2021). A similar result was presented in our study, the ICP group had a significantly more severe liver function impairment, lower levels of HDL (Table 2 and Supplemental Information 1), and a higher incidence of adverse maternal and neonatal outcomes (Table 3). Then, we further performed a logistic regression analysis of the associations between ALT, AST, ALT/AST, HDL and the risk of adverse maternal and neonatal outcomes (Supplemental Information 2 and Table 4). The results of adverse maternal outcomes showed that ALT, AST, and ALT/AST were associated with the risk of adverse maternal outcomes of cesarean section and MSAF in either Model 1 (univariate regression analysis) and Model 2 (adjusted for maternal gestational age, pre-pregnancy BMI, GWG, reproductive history, and gestational age at diagnosis) (all p < 0.05), we found the same association for HDL in Model 1 (p < 0.05), but no significant association in Model 2, which adjustment for confounding (all p > 0.05) (Supplemental Information 2).

Additionally, we also performed a logistic regression analysis of the correlation between ALT, AST, ALT/AST, HDL and the risk of adverse neonatal outcomes (Table 4). We surprisingly found that ALT/AST was a significant risk factor for the development of premature birth [adjusted odds ratio (AOR) = 4.696, 95% CI [1.859–11.861], p = 0.001], neonatal respiratory distress [adjusted odds ratio (AOR) = 4.366, 95% CI [1.452–13.126], p = 0.009], neonatal hyperbilirubinemia [adjusted odds ratio (AOR) = 4.019, 95% CI [1.757–9.194], p = 0.001] and cardiac injury [AOR = 3.500, 95% CI [1.535–7.987], p = 0.003] respectively in both univariate and multiple regression analyses. Meanwhile, as the protective factor for the development of neonatal hyperbilirubinemia and cardiac injury, HDL was also found in regression analyses [AOR = 0.315, 95% CI [0.126–0.788], p = 0.014; AOR = 0.134 (0.039–0.461), p = 0.001].

Exploring the predictive value of serum ALT/AST combined with HDL for adverse neonatal outcomes in ICP pregnant women

Table 2 showed that ALT/AST and HDL levels were significantly different between the normal group and the different degrees of ICP groups, and both were associated with the development of neonatal hyperbilirubinemia and cardiac injury (Table 4). To assess the combined predictive efficacy of ALT/AST and HDL levels on adverse neonatal outcomes, the ROC analysis were plotted in the Fig. 1, which showed the AUC value for ALT/AST independently predicted adverse neonatal hyperbilirubinemia outcome was 0.644 [95% confidence interval (CI): 53.6–75.2%, p = 0.008], the sensitivity and specificity were 50.0% and 77.3% respectively. The combined predictive efficacy of ALT/AST and HDL levels increased the AUC (0.668) [95% CI [56.3–77.3]%, p = 0.002] and the sensitivity and specificity were 47.1% and 84.0%, respectively (Fig. 1A). Similarly, we described ROC curve for ALT/AST and HDL for predicting adverse outcomes in neonatal cardiac injury, Fig. 1B showed that the combination of HDL levels predicted neonatal cardiac injury with the AUC of 0.668 [95% CI [56.4–77.1]%, p = 0.002], and the sensitivity and specificity were 41.2% and 87.1%, respectively, all of which were more efficient than ALT/AST alone in predicting neonatal cardiac injury (AUC: 0.644 (95% CI [53.6–75.2]%, p = 0.008), sensitivity and specificity were 50.0% and 77.3% respectively). In order to further clarify the predictive value of ALT/AST and HDL, we analyzed the value of TBA in predicting neonatal hyperbilirubinemia and cardiac injury in Supplemental Information 3, the results showed that the value of TBA in predicting neonatal hyperbilirubinemia and cardiac injury was lower than that of ALT/AST and HDL (AUC: 0.653, 95% CI [54.5–76.0]%, p = 0.005, and AUC: 0.662, 95% CI [55.3–77.2]%, p = 0.003). These findings suggested that ALT/AST combined with HDL may be a predictive clinical value of adverse neonatal outcomes of hyperbilirubinemia and cardiac injury.