Prevalence and risk factors of intrahepatic cholestasis of pregnancy in a Chinese population

Abstract

Studies on the risk factors for intrahepatic cholestasis of pregnancy (ICP) in a population-based cohort are lacking. We assess the prevalence and risk factors of ICP in a Chinese population. In this study, a cohort study was conducted that included 12,200 eligible pregnant women. The overall incidence of ICP in this cohort was 6.06%. With increasing maternal age, the incidence of ICP decreased in women younger than 30 years of age but increased in those older than 30. With increasing pre-pregnancy BMI, the incidence of ICP decreased if the pre-pregnancy BMI was less than 23 kg/m² but increased if it was 23 kg/m² or higher. Further analysis showed that the risk of ICP increased when maternal age was < 25 years (Adjusted RR 2.01; 95% CI 1.64-2.47) or ≥ 35 years (Adjusted RR 1.34; 95% CI 1.02-1.76). Furthermore, an increased risk of ICP was associated with pre-pregnancy underweight (adjusted RR 1.27; 95% CI 1.04-1.56), inadequate gestational weight gain (GWG) (adjusted RR 1.58; 95% CI 1.28-1.96), lower maternal education (adjusted RR 2.96; 95% CI 2.35-3.74), multiparity (adjusted RR 1.54; 95% CI 1.23-1.93), and twin/multiple pregnancies (adjusted RR 2.12; 95% CI 1.25-3.58). Maternal age (< 25 or ≥ 35 years), underweight, inadequate GWG, lower maternal education, multiparity, and twin/multiple pregnancies were identified as risk factors of ICP.

Figure 1

The relationship between ICP frequency and maternal age and BMI. (A) Maternal age in 10 categories. Age range in category 1, younger than 20.0 years of age (n = 98); 2, 20.0–22.4 (n = 617); 3, 22.5–24.9 (n = 1170); 4, 25–27.4 (n = 3117); 5, 27.5–29.9 (n = 2523); 6, 30.0–32.4 (n = 2451); 7, 32.5–34.9 (n = 809); 8, 35.0–37.4 (n = 821); 9, 37.5–39.9 (n = 279); 10, 40 or older (n = 315). (B) Maternal BMI in 8 categories. BMI range in category 1, less than 18.5 kg/m² (n = 2074); 2, 18.5–19.9 (n = 2718); 3, 20.0–21.4 (n = 2994); 4, 21.5–22.9 (n = 1836); 5, 23.0–24.4 (n = 1189); 6, 24.5–25.9 (n = 673); 7, 26.0–27.4 (n = 329); 8, 27.5 or higher (n = 387).