Materials and methods
This is a cross-sectional study of TSBA levels in pregnant women attending Florence Careggi University Hospital, a tertiary referral Maternity hospital. Healthy pregnant women at term admitted to the Obstetrics Department between 2020 and 2021 were offered participation. The reference population was defined “healthy”, after excluding women with a pathology for which there is an association with the measurement being considered.
Inclusion criteria were singleton pregnancy; gestational age at or above 37 weeks; body mass index (BMI) between 17 and 40 kg/m².
Exclusion criteria were the presence of an established diagnosis of ICP or abnormal liver function tests at any time throughout the pregnancy. We also excluded any co-existing condition of increased risk for ICP such as: multiple pregnancy; personal history of ICP; personal history of liver disease (such as history of hepatitis B and C); cholecystectomy; history of gastric bypass surgery; and the inability to provide informed consent.
Both fasting (after 8-14 hours of fasting at 8 A.M.) and postprandial (2 hours after meal at 2 P.M.) TSBA were measured. The limited time frame in which the blood samples could be sent to the laboratory, as well as the dynamic nature of the obstetrics department, was the main limit to patients’ inclusion. Not all the potential candidates eligible for the study could participate or give an informed consent. In particular, pregnant women who were sent to the delivery room before the blood sample was taken could not participate.
For each patient, both venous blood samples were collected whenever possible compatibly with the needs of the laboratory (as specified above), otherwise only one of the two blood samples was taken.
TSBA levels correspond to the sum of more than 20 individual bile acids21, and were estimated by enzymatic-spectrophotometric assay, based on microbial 3α hydroxysteroid dehydrogenase. Blood samples were analysed using Total Bile Acids Assay Kit (Sentinel Diagnostics CH. SpA, Milan, Italy) at the Careggi hospital clinical laboratory.
TSBA values were included for reference interval calculation, according to the International Federation of Clinical Chemistry and Clinical and Laboratory Standards Institute C28-A3 recommendations. An abnormal level was defined as a value exceeding the upper reference limit (97.5th)32,35, as there is no known clinical significance to low levels of TSBA. In our laboratory, the normal range of TSBA in the general population lies between 0 and 6 µmol/L.
The laboratory results were collected in a database along with maternal and pregnancy characteristics. This information was obtained upon admission, as part of the information routinely collected for hospitalization. Patients were then followed-up until delivery, and data regarding the delivery and neonatal outcome were collected.